To a point both are as bad as each other.
I'm a casual elitist
I play very very very casual in other mmos. I am in zero hurry to get to end game, am playing just the way I want to play.
However, when I get to end game, I realise that if I want to group with raiders who see raiding as their passion, I have to respect what they do, hence make sure I am adequately equipped and can play my char if I expect them to let me raid with them (mind you I am no where near what many would call a good raider, the point is, I wasn't a liability).
The problems comes in various forms and often they are valid points. For example
When someone is new to end game and certain end game players wont give them the time of day, the seasoned end gamer simply want to play with the best all the time.
Now that might seem elitist but it's not as simple as that. If your doing a hard raid that can take 2 hrs with skilled players that know their class and are equipped properly for it, why should such a player take someone unprepared, unequipped when they know that by doing so, the chances are it will cause wipe after wipe and take twice as long to do the raid (if they manage it at all). It's even worse when some bosses etc have game mechanics where they can reset/heal them selves if certain actions are done or not done correctly.
Having a player want to join such a group but doesn't want to listen to them when they say the player isn't properly equipped, doesn't want to follow orders from the raid leader etc, well I see it totally from the raid leaders point of view.
Most so called elitist players have studied their class inside and out, have spent often days grinding to get the best possible gear and have put a lot of personal time and effort into getting their character raid ready.
Then along comes mr/mrs casual, hey guys can I join your group please? The raid leader inspects them, says they need to improve xyz first and the casual gets in a strop and calls them elitist.
But, it would be a bit like if your in a sports team for whatever, you practise 5 nights a week, you have all the proper gear and every Sunday you and your team mates play a match. You don't mind new talent coming along, but you expect that if they do, they will know how to play and will have the right sports equipment. A new player turning up who isn't sure of all the rules (how to play class properly), doesn't want to listen to the team captain, complains that all they want to do is have fun etc, well I hope you can understand it from the so called elitist point of view.
I would say that the best thing such a casual player can do is join a friendly guild. My Lotro kin was very very welcoming of new players. We had our raiding team and when we invited new kin members, we explained that once at end level, some of us will be prepared to run smaller instances with them to help them learn their class etc and then we would gradually introduce them to the simpler raids and it worked very very well.
Raiders and many PvE players enjoy really hard content. Over the years they have seen MMOs cater more and more to the casual player, where you no longer need to ever group up to level (and even when doing solo content, its no real challenge). You often don't even have to really pay attention to what skill your using while you do level, you can simply button mash (faceroll) through most of the content.
And when such players ask for more group content, ask for harder solo content in various game forums, they get accused of being elitist.
I have met a few true elitist players but most are happy for time spent developing easier solo content for the players that want them, providing they can still have their harder content.
But often the casual player will throw a wobblier if there's one quest they cant do without dying as few times, or fill the forums up with complaints that it's not fair raid rewards are only available to the raiders, they pay the same to play, they should be allowed to have the same rewards too etc. And often games that raiders have invested years in, become dumbed down to the point they have zero enjoyment anymore.
A raider (or PvE) player that has been through that in a game, is naturally wary when more casual players start complaining about xyz. For example, in ESO, when I first did the Mages and fighter guilds quest, I died non stop and I was really really pleased that at last I've found a bit of content I need to think about, something I cant simply rush in and do anything.
Last beta I did the mages guild quest on a new character, level 8, ran through it first time, had to use just one potion, no other healing at all. I actually found the first room (don't want to give spoilers) more of a challenge than the boss. I don't know if it's because I knew how the boss worked, but I suspect they made it easier due to the barrage of complaints about how hard it was. And for every one complaint that it and the fighters guild were too hard, there were about 5 replies saying it wasn't.
It was simply a matter of working out the mechanics of both the bosses and if you couldn't work it out for yourself, a simple google would tell you how to easily complete them, I say easily, it might take you 4 or 5 attempts or if your not used to blocking etc, you might need to do it a couple of levels above the level it's aimed at, but there was no need for either of these quests to be dumbed down. This is why so called elitists get very frustrated at the so called casual.
From the casual players point of view, they have joined a game, they are paying to play, they don't really understand their class yet as they are new. They come across they first thing that needs grouping for. They ask if anyone wants to do it. They get a few replies. Then a few things can happen, here are some examples.
1) They start to try and explain they are new, no one pays them any attention and people are already flying in killing everything, rushing through it, not allowing them to see what's going on at all, not allowing them to learn anything about playing their class etc etc etc. A really frustrating experience for them.
2) Point number 1 happens, but because you don't know what's going on, the group leader kicks you without warning, again very very rude and frustrating.
3) People shout at you in group chat and are arrogant and rude to you because no one bothered to explain anything to you and expected you to be psychic, again very frustrating.
4) People ask you what weapon/armour/stats you are using and tell you you are wrong to use it and there's only one choice to play your class properly and that is their way. Very very very very annoying
and many combinations of the above.
5) You find yourself in a good group consisting of a guild that was a player short, hence invited you, a guild of good mannered people, that realise you are new, take the time to explain everything to you, you have great fun with them and at the end, the guild leader invites you to the guild, and you have many years of fun with them.
I played Lotro for nearly a year before I joined a guild, simply because every tine I joined a pug (pick up group, random players looking to group) I experienced 1 - 4 of the above and Lotro is supposed to have a more friendly community than most. Once I was stuck soloing a quest mob and another couple of players nearby asked me to group, as I had died numerous times, I reluctantly accepted. By the end of that quest I was a guild member, went on to become officer, and only a couple of weeks ago received a nice parcel of cookies from a fellow officer who lives in the US that she baked herself.
I'm not sure if that helps explain why casuals or elitists don't get on or not, I'm just trying to explain how I see it from both sides.
I think ESO is a bit different from other mmos,on that while there is the huge PvP world, a lot of the game has been designed for those that love TeS. I personally intend taking my time to level up, not caring if it takes me two years, I'm going to get into the lore, fishing, crafting, I want to discover the skyshards, lore books, treasure map locations etc for myself, I don't want to read them off a web site.
I'm going to equip my character with exactly what I want and use exactly what skills I want too.
But, when I do finally get to end level, or if I find that when I do do group content as I'm levelling, I am a liability, I will look at getting the skills needed (rather than what I enjoy most) for when I'm grouped