There are all kinds of T's and I'm sure a good fraction of them are just plain bad at their job. I'm sure that a % of T's would not "understand" me, and a fraction would, and some in the middle... just based on their own transference or superficial stuff. What I'm getting to is this one therapist shouldn't make you feel unhelpable, especially when the same therapist is being vague about why they terminated therapy.

It could be the therapist didn't think you had a good enough relationship to really trust them and do the work. Could be you had issues they were not familiar with, and didn't think they would do a good job of helping you. Could be some of your beliefs clashed with theirs and they couldn't reconcile them, and also cant tell you what and why because it's personal (i.e. if you are a devout Baptist and they aren't religious.) Bottom line is, IMO, it could be any number of things and only one of which is that you are unhepable. I actually doubt any therapist would think someone is totally unhelpable though, so I think that's the least likely possibility.

Try not to sweat it. I know that's easier said than done. You just need some people on your side and in your corner. You need a therapist who believes in you! This T just doesn't sound like a good one. Find one with decades of experience, that will increase the likelihood they'll be good at their job.