At least the online class cheating increases fairness. Now you can cheat without having the money to purchase a bogus disability claim. For many years now, all the well-off schemers have been taking tests with twice as much time as normal. Nobody in academia dares to push back at this fraud, out of fear that they might be pilloried for failure to accommodate. Honest students usually aren't even aware of just how unfair the system is. It affects high school, college admissions tests, and college.
The whole system is put at risk by the fraud. Grades become less meaningful because we've added a randomish negative signal. That devalues everything.
I had a lot of mental health issues and I registered with my school's accessibility services. I was surprised I could get extra time on tests, extensions, etc. so easily. Unfortunately, none of those accommodations were even helpful for me. An extension would just make me fall further behind on other work, and I didn't have test anxiety or a disability which would prevent me from taking tests quickly (though I was offered this accommodation anyway).
The only accommodation that I took once or twice was having a teacher re-weight marks from a missed assignment to other assignments, which was only good for me if I was going to do well on those other assignments. I think for mental health, the most important things my school did for me weren't even accommodations. They were: letting me reattempt courses any number of times, letting me take a year off without even having to notify them, letting me take a reduced course load, and stuff like that. These things give no advantage to students who utilize them, but can make a world of a difference to students who need them. Without them I'd have failed my degree, but now I'm mentally healthy and I'm going to graduate soon.
Anyway, it's shitty that some people abuse accommodations, but most of them don't give them an advantage over other students, and some students do need them, so getting rid of them is not really a solution. The main one that would give an advantage is increased test time (the solution to which is to write exams where students already have plenty of time -- the majority of my profs already do this).
As for the whole system being put at risk, I think the whole system is going down the shitter anyway. Why do I need to pay thousands and thousands of dollars a year for an education which could easily be delivered for less than a tenth of that price? Prestige? I don't think universities will survive the modern Internet outside of programs which need hands-on lab experience.
Getting rid of accommodations in general is not the right thing to do, and I am very glad that you were able to get the sorts of support you actually needed, as opposed to just the cookie-cutter extra time on exams.
That said, giving time and a half or double time on exams to anyone who takes the time and money to track down a compliant enough medical professional to diagnose them with ADHD is not the right thing either. And yes, some people really do have ADHD and need various support, not limited to extra time on exams, to succeed in the school environments we have created. But _so_ many people are diagnosed with ADHD who have nothing of the sort...
Anecdotally, my acquaintances who teach at elite liberal arts colleges say that 25-40% of their students nowadays are receiving extra-time accommodations, a sharp rise over just 10 years ago. It's possible that the prevalence of ADHD and various mental health issues really is that high amongst high-performing teenagers nowadays; the college admissions crapshoot and lead-up to it surely is not helping with mental health. But I find it much more likely that there's a significant amount of gaming the system going on, unfortunately.
This would fix the problem: if a student in a course gets an accommodation, all students in that course get the accommodation by default. It would be OK to opt out, so for example we don't force everybody to use a screen reader. (but you get one unless you opt out) Clearly this solves the extra-time fraud.
The problem with this is that then the legitimate ADHD students are then at a disadvantage to the other students, as they can't use the time as effectively as the other students.
The whole system is put at risk by the fraud. Grades become less meaningful because we've added a randomish negative signal. That devalues everything.