Many games have had open world style, and while thier original offerings were closer to the first open world style, if you go play them, they are not nearly as much fun as their more recent open world games, or even other games of their time (compare Arena to Ultima 6 or wizardry 5).
If you look at the Ultima or Might and Magic series (6 in particular from both franchises oddly enough), they are both very open world games, that let you explore in many directions. In M&M, you definately have to use better tactics if you go certain directions before others, but that is part of the fun. In Ultima, the level progression is flat enough that you never entirely outgrow the initial difficulties by large amounts. Bethesda hardly invented the genre, but they certainly have been leading it for the last decade or so. The Wizardry series is another good older game with a lot of open world exploration style in I think around wizardry 5 or so onward.
Its actually kind of funny that if you go back enough years, open world exploration style games were the more popular ones, then RPGs sort of migrated to a very JRPG feel following success of games like final fantasy, and now with bethesda leading the way, open world style is becoming increasingly popular again. Either way its great because the style has always been my favorite.
Grinding is often avoidable through good tactics, thats probably the one thing I do like about leveling systems in games, is being able to figure out a way to complete an area or boss well before it was intended to be beaten through interesting tactics. The weapons in ff7 are a good example in that good materia selection and tactics meant far more than leveling, or at least mitigates that amount of grinding you needed to do considerably.
Overall, the FO4 system achieves its goals, level wise. I dont feel like there is any point in the game where I thought to myself, "I'd really like to do this quest, but I need to go grind out some levels first". Or in general a feel that you need to go level up before attempting anything. You just play the quests how you like, and you will be fine. There was a bit of 'oh god this is stupid easy' when doing quests in areas you had already visited though, which was unfortunate. In general, while the enemys level up with you, they feel weaker at every level, and once you reach around 25ish, nothing feels particularly challenging again. And of course if you wear power armor the whole game is trivial, but thats a different thread entirely.