Well, I've been using Nvidia cards for years, and the last time I built a new computer (some months ago) I had a hard time deciding whether to stick to Nvidia or switching to AMD. Eventually, I chose to stay with Nvidia, because getting a new AMD card (apart from the fact that there seems to be no budget AMD cards...) seemed like a lottery in terms of having a stable Linux desktop environment, being my best bet to get an older generation card (RX570 or RX580), that had not much availability and they were overpriced here.

As for slowing down Linux desktop progress, I think it's not Nvidia's fault: you could always get a card from another vendor, although the alternatives were not as good. Well, maybe those other vendors are to blame, and not Nvidia...

I'd say it's their fault, since due to the above situation, there were a lot of Linux users with Nvidia cards. Nvidia didn't care to upstream things and that caused them not to support Wayland and many other modern use cases for years.

Today it's less relevant, since usage of Nvidia on Linux is gradually dropping, so their damage to the progress is also diminishing thanks to that. Wayland compositors' developers can simply say - we don't support the blob and don't plan to and be done with it. In the past it was much harder, due to how many Linux users had Nvidia still while alternatives were way less viable.