kmalloc

That's actually worse than the 3dxp business case. Because in the future where 3dxp had worked, the argument was that it came in VAST quantities. If I remember correctly, the argument at the time was for a 2 socket machine with 128GB of DRAM, 8TB of 3dxp and some amount of NVMe storage.

So you might reasonably want to say "Hey, give me 4TB of slow memory" because you'd designed your algorithm to be tolerant of that latency.

And then 3dxp also had the persistence argument for it; maybe there really was a use-case for storage-presented-as-memory. Again, CXL as envisaged by you doesn't provide that either. It's just DRAM behind a slow interconnect.