(reply to Zoomer from further down, moving up because I ended up writing a lot)
This experience is largely a misalignment between what AMD thinks their product is and what the Linux world thinks software is. My pet theory is it's a holdover from the GPU being primarily a games console product as that's what kept the company alive through the recent dark times. There's money now but some of the best practices are sticky.
In games dev, you ship a SDK. Speaking with personal experience here as I was on the playstation dev tools team. That's a compiler, debugger, profiler, language runtimes, bunch of math libs etc all packaged together with a single version number for the whole thing. A games studio downloads that and uses it for the entire dev cycle of the game. They've noticed that compiler bugs move so each game is essentially dependent on the "characteristics" of that toolchain and persuading them to gamble on a toolchain upgrade mid cycle requires some feature they really badly want.
HPC has some things in common with this. You "module load rocm-5.2" or whatever and now your whole environment is that particular toolchain release. That's where the math libraries are and where the compiler is.
With that context, the internal testing process makes a lot of sense. At some point AMD picks a target OS. I think it's literally "LTS Ubuntu" or a RedHat release or similar. Something that is already available anyway. That gets installed on a lot of CI machines, test machines, developer machines. Most of the boxes I can ssh into have Ubuntu on them. The userspace details don't matter much but what this does do is fix the kernel version for a given release number. Possibly to one of two similar kernel versions. Then there's a multiple month dev and testing process, all on that kernel.
Testing involves some largish number of programs that customers care about. Whatever they're running on the clusters, or some AI things these days. It also involves a lot of performance testing where things getting slower is a bug. The release team are very clear on things not going out the door if things are broken or slower and it's not a fun time to have your commit from months ago pulled out of the bisection as the root cause. That as-shipped configuration - kernel 5.whatever, the driver you build yourself as opposed to the one that kernel shipped with, the ROCm userspace version 4.1 or so - taken together is pretty solid. It sometimes falls over in the field anyway when running applications that aren't in the internal testing set but users of it don't seem anything like as cross as the HN crowd.
This pretty much gives you the discrepancy in user experience. If you've got a rocm release running on one of the HPC machines, or you've got a gaming SDK on a specific console version, things work fairly well and because it's a fixed point things that don't work can be patched around.
In contrast, you can take whatever linux kernel you like and use the amdkfd driver in that, combined with whatever ROCm packages your distribution has bundled. Last I looked it was ROCm 5.2 in debian, lightly patched. A colleague runs Arch which I think is more recent. Gentoo will be different again. I don't know about the others. That kernel probably isn't from the magic list of hammered on under testing. The driver definitely isn't. The driver people work largely upstream but the gitlab fork can be quite divergent from it, much like the rocm llvm can be quite divergent from the upstream llvm.
So when you take the happy path on Linux and use whatever kernel you happen to have installed, that's a codebase that went through whatever testing the kernel project does on the driver and reflects the fraction of a kernel dev branch that was upstream at that point in time. Sometimes it's very stable, sometimes it's really not. I stubbornly refuse to use the binary release of ROCm and use whatever driver is in Debian testing and occasionally have a bad time with stability as a result. But that's because I'm deliberately running a bleeding edge dev build because bugs I stumble across have a chance of me fixing them before users run into it.
I don't think people using apt-get install rocm necessarily know whether they're using a kernel that the userspace is expected to work with or a dev version of excitement since they look the same. The documentation says to use the approved linux release - some Ubuntu flavour with a specific version number - but doesn't draw much attention to the expected experience if you ignore that command.
This is strongly related to the "approved cards list" that HN also hates. It literally means the release testing passed on the cards in that list, and the release testing was not run on the other ones. So you're back into the YMMV region, along with people like me stubbornly running non-approved gaming hardware on non-approved kernels with a bunch of code I built from source using a different compiler to the one used for the production binaries.
None of this is remotely apparent to me from our documentation but it does follow pretty directly from the games dev / HPC design space.