From a per mm2 performance standpoint things absolutely have slowed considerably. Gains are primarily being eked out via process advantage (which has slowed down) and larger chips (which has an ever-shrinking limit depending on the tech used)
Chiplets have slowed the slowdown in AI, but you can see in the gaming space how much things have slowed to get an idea of what is coming for enterprise.
This isn't true in the AI chip space (yet). And so much of this isn't just about compute but about the memory.