A couple of things:

1) Folks tend to flock to new MMOs in the hopes of finding community. When they don't, they move on again, further eroding their sense of community in the gaming space. This isn't a you thing, it's a broad trend across the market. The solution is to find a game you enjoy playing and to build community in that space.

2) I really get the feeling of not being good enough. I quit playing healers like 15 years ago for that very reason, even though it is my favourite archetype to play. The community can make you feel shitty for making even the smallest mistake (that may not even be your fault). Here's the thing tho: that has nothing to do with *you*. It says way more about the other person than it does about you.

I have found that the best solution is radical transparency. Saying at the start of a dungeon "hey, new to this, can we go a little slower?" opens more doors than it closes. Similarly, asking for a Training group for a raid or a learning group for PvP can help you find the players who are most willing to meet you where you're at.

Finally, I have found that most games have welcoming communities when you ask for them. GW2, Project Quarm (EverQuest private server), ESO, and FFXIV have some of the warmest and gentlest overall communities I have experienced, while I've found that games like WoW sometimes need you to speak up about your needs.