I like how people just ignore OP's wishes and tell him to join one anyways. If my real life friends didn't want to make an FC I would be in the same boat as OP. It's much more enjoyable to just not be in a FC and avoid the cringe, toxicity, spam, or all of the above. Sometimes it's just not worth the buffs especially since squadron manuals are a thing.

At the moment I would just make room on the blacklist starting with the obvious gil spammer names since those accounts usually go dark after a while. Being forced to go /dnd and blocking out all correspondence is annoying, but there aren't that many options available currently. Making your own private FC would be nice but you'll have to deal with getting people together to start it up and remove them afterwards. If you have a friend willing to help they can make alts to fill out the required starting members.