There are still some Mom & Pop shops that will put together a custom machine for you, but if you are talking about completely new computer architectures that aren't compatible with anything else the barriers to entry are so much higher. The expectations are miles away from where they were in the 80s. Back when everybody sucked it didn't matter that your first product barely works and had few capabilities. Today your competition is Intel, AMD, nVidia, Apple, etc... Trying to stand out compared to the giants is much harder. Plus you have to deal with the software. Making a DOS clone is no problem. Making a Windows 11 clone is orders of magnitude more work.
