The 8 GB will see you have to resort to low/med textures on occasion which look horrid, as well as having to lower other settings even though you'd have the processing power for them. That's on top of AMD cards needing even more vram than Nvidia. If you don't think the 8GB of vram is a problem then might as well get a 4060 so you can enjoy DLSS. Can't imagine being stuck on low settings AND FSR @ 1080p - yuck!
Yeah I think that game may be a bit of an extreme example, but that being said I have personally experienced plenty of games that go over 8gb for example.
Both Cities Skylines, Fallout 76 (unmodded), Fallout 4 (admittedly some mods), the new Flight Sim eats everything at the moment, there are others as well, at 1440p anyway.
You can have all the GPU power in the world but if you hit the memory limit you are going to get a significant hit in performance. I would rather be maxing processing ability, even if not utilising all the memory, which is at least, more consistent, than having the huge jumps from VRAM limit.
I think it very much depends on screen resolution as well.
A 3070 is an absolute prime example of that, I had one. It had plenty of GPU power, but then you would hit the limit and you game goes from 140 FPS down to like 60-70, for a few seconds, then back up. Checked and surely enough hitting 100% GPU memory. It's such a shame, because had that card shipped with even 12 gb (it should have done in my opinion) there would be less occasions and I think 12gb would have been more balanced for that GPU, the AMD equivalent did. The cynic in me, well, not even really being that cynical is that Nvidia do that on purpose to try to keep you upgrading more regularly. 8GB was clearly not enough for the power of that GPU.
Anyway, it will be a while before I max 20gb on my 7900xt, and a while before I buy another Nvidia card.
In my opinion a gaming GPU should have a minimum of 12GB unless it is a really low end/budget card, if I am honest, I think we are heading towards 16gb for 2025 to being the new acceptable minumum of a mid range GPU.