It's not "optimistic", it's actually happening. Don't forget that GPU compute is a pretty vast field, and not every field/application has a hard-coded dependency on CUDA/nVidia.
For instance, both TensorFlow and PyTorch work fine with ROCm 6.0+ now, and this enables a lot of ML tasks such as running LLMs like Llama2. Stable Diffusion also works fine - I've tested 2.1 a while back and performance has been great on my Arch + 7800 XT setup. There's plenty more such examples where AMD is already a viable option. And don't forget ZLUDA too, which is being continuing to be improved.
I mean, look at this benchmark from Feb, that's not bad at all:
And ZLUDA has had many improvements since then, so this will only get better.
Of course, whether all this makes an actual dent in nVidia compute market share is a completely different story (thanks to enterprise $$$ + existing hw that's already out there), but the point is, at least for many people/projects - ROCm is already a viable alternative to CUDA for many scenarios. And this will only improve with time. Just within the last 6 months for instance there have been VAST improvements in both ROCm (like the 6.0 release) and compatibility with major projects (like PyTorch). 6.1 was released only a few weeks ago with improved SD performance, a new video decode component (rocDecode), much faster matrix calculations with the new EigenSolver etc. It's a very exiting space to be in to be honest.
So you'd have to be blind to not notice these rapid changes that's really happening. And yes, right now it's still very, very early days for AMD and they've got a lot of catching up to do, and there's a lot of scope for improvement too. But it's happening for sure, AMD + the community isn't sitting idle.