I'm not sure what the take rate of FSD is from back then. But I would assume there are several factors... arbitration clause, most people are not litigious, general sense of just accepting FSD as it is and moving on, etc. It is also hard to quantify what your damages are because you did get certain aspects of the FSD so it's not like the full FSD isn't there.
As for myself, I got my car in Oct of last year and made my decision based on what FSD could do at that time. I passed on FSD but would have gotten enhanced auto pilot but waited too long. I am using the subscription version but mainly for the ability to lane change without disengaging. I suspect a lot of people who are upset at their FSD purchase are the direct result of Tesla's advertising at that time. They were told full FSD would be coming soon. Even last year when Elon raised the price to 10k he intimated the increase was because full FSD was imminent. I believe the verbiage in the older purchases over promised and perhaps did not have the same disclaimer as what is in the current contracts. People bought into Elon's hype and their marketing either didn't or didn't do enough to inform buyers of the time frame or capability.
There is also the possibility those who were persistent and got their refund never posted to the forums. They simply got their refund or credit and moved on.
I'm no lawyer, but even when I bought FSD (2018) I knew Tesla was committing fraud. I simply ignored the whole fraud thing, and bought it anyways.
A lot of us like myself who paid for FSD knew the way it was being marketed, and the timeframe given for it was completely fraudulent. That it would never be capable of doing what Elon said it would be capable of let alone on the time frame given by Musk.
I often avoided having a conversation about FSD to friends/family interested in a Tesla because it's an awkward conversation to have. It would have been much easier if Elon promised something more tangible.
Now days it's a lot easier to have a conversation about because FSD is available as a subscription. I fail to see how Auto-Lane change is worth $200/month to someone, but they're not taking your money while promising you anything more.
My advice for someone who doesn't want to commit fraud:
Don't sell people things you don't have control over.
You can't sell a person a planet for that same reason. You have no authority over the ownership of a planet.
You can't sell a person a self-driving car because you have no authority over whether your self-driving car will even be allowed to be self-driving.
Even pre-selling a L2 semi-autonomous car is risky because regulatory bodies might not allow the full feature set of what you promise.
You should probably complete the feature first, and once you have regulatory approval then you can sell it.