Don't feel pressured to join an FC you're not comfortable with. Join one when you feel comfortable to.

That said, aside from beneficial things having an FC gets you access to (Such as the buffs), just being around a lot more people is a great help. Being able to chat with people, ask for people to come run content with you, etc; it's a huge relaxer and adds a lot to the game, I think. FCs aren't solely endgame oriented - although there are inevitably some out there that are specific to that. A lot are plenty casual, with lots of members levelling or helping each other through content or even just being social and hanging out.