I think people are projecting massively when they say that they are 100% sure it's jealousy etc. It might be. Or it might not be. We've had grade 8 singers in our choir, and they are by no means the best at choral singing, however good they might be individually. One of them is terribly flat most of the time! It probably wasn't so obvious when he was singing solo as he didn't have to fit in with others. Some of them are massively loud, and really don't notice that they're not blending. Or don't notice that they are making mistakes because they can't even hear the rest of their section (or aren't listening). They get wrong notes, or rhythms, or words. And can't tell, because they are louder than everyone, so their mistakes don't stand out to them. It's not that they aren't good singers, or that they aren't liked, but they can be very difficult to have in the choir. On the other hand, when they really work at it, they can also be huge assets, because they are strong singers, and that can be really helpful. But it has to fit in and adjust. So don't assume it's jealousy. It might be that others do find a particular voice very difficult because of volume, blending, tuning, or accuracy issues, rather than being cliquey or jealous.
None of that excuses treating someone badly and not giving them a chance to correct it, though. It could be handled much better. And it could be that it's jealousy or resentment of an outsider coming in. But there are lots of reasons that it might not be, too. so I'd say, stay open minded to the possibility that your voice doesn't fit at the moment, and if you can find a choir you want to join - or if you want to carry on in this one - see if there are things you can do to blend in better. What does the rest of your section sound like?
I do also know of people who starting singing much more loudly as they lost hearing slightly, and they were not particularly old. They just didn't realise how loud they were (and off-putting as a result, sadly).
It could be all sorts of things, including cliquey, mean people. But maybe there are other reasons, and if you would like to be part of it, maybe it will just take time and asking what you could do to improve. I know that our choir might seem cliquey to people, partly because we don't have a tea break, and thus it takes a very long time to get to know people, because people tend to gravitate to talking to those they know in the short time we do have for socialising, because there's so little time to catch up otherwise. I wish we did have a break, as I think it would help. We tend to get to know newer people on occasional social events, but it takes quite a while for those to happen, because they're not formally arranged by the choir or anything. We also aim for a very high standard, despite being amateurs, so it isn't just for fun, and some people who want that might find that it's disappointing.