Some people wanted to use video cards with unsigned drivers. The hardware Mfr said “disable this malware blocking security feature in order to use our hardware”. As it happens most people with exotic video cards are avid users.

They disabled the malware protection and got killed by the malware.

On other platforms, those cards aren't "Exotic" (I run Premiere Pro on Windows 10 with a pair of 2080Ti cards for rendering. Premiere and After Effcts _fly_!

One problem is that Apple abandoned the Pro market, but some users are very loyal.

They're exotic in that their manufacturers can't be bothered signing their drivers. But at least there are drivers.

They're also exotic in the sense that only a very small proportion of the overall user base cares/requires them.

There are supported video cards / TB3 video systems that are natively supported but at the moment they are possibly even more exotic in the sense of shipping in low volume (per your second point). I really don't like "apple abandoned the XXX market, which I am in and wish they had just the right product for ME" statements but in this case, I think your comment is unfortunately correct.