To add a few things, repeat what already people said to you.

i feel like the issue might lie with me and how I deal with my relationships and other people’s emotions

It is.

These people have mental health issues but aren’t doing anything to help themselves

You aren’t responsible for thier life, nor feelings and actions, if they get mad at you for not taking them to the concert, its thier problem, not yours

What you need to do is to believe that you are independent person and are not responsible for other feelings and thoughts, you should be able do whatever you want to do, without thinking “what if this person didn’t like that?” This takes practice, but if you do it, be aware when this happened and imply it everytime, you will endup with this believe, it is a long process, and don’t worry there is no failure.

Right now if you can’t cut those people off, accept them, deal with them, set boundaries, and show it to them, if they didn’t respect it, you can also deal with that, you know how best, but it must be you being satisfied.