Software stability too. Especially for most vulnerable groups of users like beginners or my fellow blind users. We depend on audio (and Braille sometimes), and this is one of the most unstable things in Linux. Imagine if you booted your computer and prayed for your monitor to work correctly this time. this is it for us. I can link you a series of article one smart blind guy wrote, and he knows what he is talking about because he spent years on Linux desktop. If you, folks who want Linux desktop to be a real thing and not a geeky toy, make it accessible for everyone, it will succeed. Othersie… no, sorry, I need my PC to work, hence I use Windows.

I'm taking notes while reading.
1. Accessibility *is* a technical problem, not (only) a social one. To make something as huge as an OS accessible means, at least: A) To expose accessibility APIs on every plan of existence of the OS; B) Develop a decent screen reading solution (see JAWS or NVDA for Windows); C) Develop a decent screen magnifying and color altering solution (see ZoomText for Windows); D) Harden audio stability, so that a trivial update won't break your audio system; E) Develop a solution for people with motor disabilities that would allow decent voice control (see Dragon Naturally Speaking, for instance). That is an absolutely technical endeavor. You'd say Linux has Orca screen reader and you are right, but it's developed de facto by Joanmarie Diggs. Alone. No, of course, there are some people sending PRs, but do you see the difference between a paid solution like JAWS or even a community-driven solution like NVDA on the one side and a screen reader developed by one (brave and genius, but one!) person on the other? Again, I really admire Joanmarie, but she does need help, and I mean, lots of help.
2. Mobile. It's yet another challenge because tactile screens accessibility is something else than keyboard accessibility, be it terminal or GUI. Apple (no matter how I hate their policies) already solved many problems, hence the most common combo in the wealthier blind community is Windows + iPhone. Who would do the same for Linux? Up to you (in plural) to decide.
3. Toxicity of the community. I'm really sorry to admit, but open-source community is very often either toxic or indifferent. When I or one of my blind fellow folks open an issue about "X is not accessible at all, please fix it!" (where X is anything from a small web-based solution to the whole LibreOffice Calc), guess what we get? "Send a PR!". Heck no, putain de bordel de merde de… — excuse my language! I cannot spend my whole life to dig into undocumented code then send thousands upon thousands of PRs, then beg their supreme highness of developer to please merge it, then wait till it's released. I need to work, to eat and to feed my family, including cats. Hence… I use Microsoft because it just works, and if there is an accessibility bug, it gets fixed, — not always super mega fast (like in Visual Studio Code, kudos to them!), but it *is* fixed. Unlike with open-source, sorry.