While it took a while to come up with a better base chipset to replace OCS/ECS, the engineers were still belting out some fantastic designs, most of which were squished by upper management.
The above was a really good case study in business ecosystem dynamics.
When the Amiga 1000 came out, it was alien technology -- probably 10 years ahead of its time. The Amiga OCS chipset's graphics and sound hardware of its contemporary competitors look like historical artifacts, and it's OS was an actual pre-emptive multitasking operating system, not just a glorified disk loader.
However, any company in the world could design, build, and sell a new PC sound card or a new PC graphics card, any many of them did. The PC sound and graphics cards continued to suck (relative to the Amiga) for quite a while, but simply due to the fact that so many different companies had hired so many engineers to work on developing them, they improved every year, and eventually surpassed the capabilities of the Amiga sometime in the mid-90's.
Amiga's engineers were undoubtedly some of the most talented on the planet, but their small team eventually couldn't compete with the sheer numbers of PC-based engineers. By the time AGA came out, the writing was on the wall: An open system that gains traction will eventually outgrow and out-innovate a small, closed system, no matter how awesome the skills of the closed systems' engineers.