It's already happened, people just haven't realized. iCE40-UP5K costs a few bucks, needs minimal support circuitry, and is supported by FOSS toolchains (yosys). Fun packages like the pico-ice bring it all the way down to the entry-level arduino crowd. It just doesn't have the marketing mindshare.
Funny enough it is available on an UPDuino board: https://tinyvision.ai/pages/the-upduino
A few times over the past decade I wanted to start with a side project where I design and develop a CPU.
I bought a relatively cheap artic 7 board with 33kLUT and whatnot which I know people have used to implement risc-v implementations on.
But then I always lost my patience on the tooling.
For a side projects these days I need something comfortable. Something that that I can easily switch my context to without having to juggle VMs and installing unfriendly tools and use horrible IDEs