It's not ideal but I'm pretty sure CUDA didn't support everything from day 1. And ROCm is part of AMD's vendor part of the Windows AI stack so from upcoming gen on out basically anything that outputs video should support ROCm.
[1]https://www.gamesindustry.biz/nvidia-unveils-cuda-the-gpu-co...
[2]https://www.tomshardware.com/news/amd-rocm-comes-to-windows-...
AMD only claims support for a select few GPUs, but in my testing I find all the GPUs work fine if the architecture is supported. I've tested rx6600, rx6700xt for example and even though they aren't officially supported, they work fine on ROCm.
AMD had a big architecture switchover exactly 5 years ago, and the full launch wasn't over until 4.5 years ago. I think that generation should have full support. Especially because it's not like they're cutting support now. They didn't support it at launch, and they didn't support it after 1, 2, 3, 4 years either.
The other way to look at things, I'd say that for a mid to high tier GPU to be obsolete based on performance, the replacement model needs to be over twice as fast. 7700XT is just over 50% faster than 5700XT.
https://rocm.docs.amd.com/projects/install-on-linux/en/lates...
https://en.wikipedia.org/wiki/ROCm#:~:text=GCN%205%20%2D%20V...
Stable Diffusion ran fine for me on RX 570 and RX 6600XT with nothing but distro packages.
I agree that the official support list is very conservative, but I wouldn't recommend pre-Vega GPUs for use with ROCm. Stick to gfx900 and newer, if you can.