It's crazy to see just how far they've come from the first console to the latest and all the lessons they've learned along the way. https://www.youtube.com/watch?v=ph8LyNIT9sg (Some Playstation 5 architecture highlights).
Well, as much as I would love to share the excitement, all they've come to is what essentially amounts to another gaming PC. Not sure how 'far' this is, but clearly all innovation happens now on the PC side. (It almost seems now that the fact that the earlier Playstation models and other consoles had the custom architecture that was different from PC may have had to do with the need to provide enough power in a small…
The now defunct fixed function pipeline was still being formalized in PCs, let alone consoles. Each console was a massive exploration into what could be done and who could make the best SDK for that hardware to entice developers to make games.
The fact that all modern consoles and PC's are similar should be applauded. It's the culmination of decades of hardware and software learnings, standardized into the optimal hardware for graphics and game performance.
The fact that they all found what they needed in a similar architecture footprint is good for hardware design, good for developers, good for business, good for porting, good for optimization, and finally, good for performance.
Sony, Nintendo, and Microsoft are no longer able to design the latest and greatest chipsets. The complexity is just too much for them to reasonably pay to do so. That's why AMD does it for them. Why would you reinvent the wheel when someone has already spent decades making Ferrari's and is begging you to use their engine at a discount, bulk manufacturing included?
Back during the PS1, Sony had a heavy hand in the graphics card design. Not as much anymore. They tell AMD what they want to do and AMD eschews an existing chip to do it for them.
I know it sounds less glamorous, but honestly, it's the most remarkable thing I've ever seen in the history of modern manufacturing, short of landing on the moon. Having one company able to provide chipsets for any and all applications, including gaming at a practical whim seems pretty amazing.
tldr; The consoles are all the same because AMD/nVidia are so much better at hardware design than Microsoft/Sony/Nintendo that it's not even funny anymore. If someone has the latest and greatest already available for licensing, just buy it and get on with making amazing games.