The farthest I have gone with the main quest is Shattered, but I think I'm sort of stuck with the Railroad quests because as far as I can tell they aren't offering anything else because I haven't gone far enough in the main story quests. Can anyone verify this without giving spoilers? Thanks.

All quests from the available factions stop at a certain point and can not be continued until progression is made in the main story. You'll just keep getting their generic repeatable fetch quests.

As for the question in your post. That is hard to say, just depends on the type of player you are. The game continues anyway even after you complete the main quest, obviously though based on your decisions it locks you out of further interaction with certain factions. Some folks hit the story up right away, and some people haven't even done the main quest yet despite having had the game since it's release (know a guy who only just now went to diamond city) In my opinion though, it doesn't matter much to me, the main quest is a bit thin and the meat of most Bethesda games of this nature is more about exploring your surroundings honestly.

Keep going in the main quest. There is no reason to hold off continuing (in my opinion) until you've completed:

The spoiler gives no details, but names a quest you haven't reached yet.

Spoiler

When you gt to a certain quest, you'll have to ultimately chose which faction to side with and which to become enemies. Save and remember this game file. Having the option to interact with these factions is always a plus, while some will no longer exist after completing the game.