I don't think AMD needs to support 5+ year old GPUs personally. And all the recent generations are already practically supported.
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.
I'm on a 5+ year old GPU, because I don't trust AMD to offer a compelling GPU that actually works. An RX 7 570 is good enough for the little gaming I do. It mostly acts as an oversized iGPU that has good Linux drivers, but since AMD is not supporting ROCm on this GPU, there is no need to hurry on upgrading to a better GPU or to get my feet wet on running things locally on the GPU like Stable Diffusion, LLMs, etc.
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.