If a person has a disability that can very much affect how well they perform they should try to group up with people they know if possible. Not just because people you know would be more likely to be supportive if you're having difficulty, but also because pugs have no way of knowing if you're disabled unless you tell them. Even if you do, explaining a disability can be lengthy and some people would assume it's a lie designed to get away with certain things...which of course can lead to drama.
I'm disabled but I certainly wouldn't ever reveal this to a pug group. I don't really want to be in the position in which people would be doubting the validity of my claim. It's too much of a headache. I don't join pugs to debate about medical issues, and pugs don't pug to carry the heavy burdens of someone else, disabled or otherwise.
Just like anyone else disabled people are responsible for what they put other people through. If you're having a really really bad day with your disability and expect pugs to just carry you...that's not cool. If I'm having a really bad day I play with people I know, stick to content where I wouldn't have difficulty, or entirely avoid playing. Adjusting what you play and with who, is taking responsibility for your impact on other people.
Everyone needs to be realistic about what they can achieve as a player. Whether you're new, rusty, not particularly skilled, or disabled. Unfortunately not everyone has the potential to be an all-star raider because life is not fair. We're not all dealt the same hand. But what also isn't fair is expecting people to carry you just because you are unable to or are too lazy to improve. Adjust your expectations whether that means realising you have much to learn, or that life dealt you a hand that makes you peak earlier than some others.
If you are below the requirements to do certain content but still badly want to do it, find a group that is okay with dealing with your particular skillset. Not only does this mean you won't be putting pugs in an unpleasant position, you will most likely find that you have a far higher success rate of completing content. You won't be getting kicked so you would get the opportunity to learn to deal with your limitations better, or even find ways to overcome them.
That being said a lot of players need to adjust their expectations of other people. I can't even begin to count the amount of times I have seen people in the forums complain about players in normal mode DF that wouldn't parse at least very high green. They rarely explicitly say it but when you see the things they complain about players not doing, pretty often they're asking for far above the requirement of the content. Personally I adjust my judgement of other players based on the content we're doing. I'm very forgiving in normal mode, but in ex or savage my expectations rise very significantly, because that content requires far more from players than normal mode.
Yes I know genuinely awful players exist, even those awful by normal mode standards...but that is a problem with literally every multiplayer game. Great, bad and everything in-between exist in every gaming community. No matter how many tutorials are in games, how many great guides there are, there will always be people who fall between the cracks that make you wonder how they got as far as they did. It sucks but this will never change. It's just how people are.
Thanks for coming to my Ted Talk :P