For all practical purposes we have that - they’re called FPGAs. For digital logic, the performance you can get out of an FPGA is as good as any low cost effort to actually fabricate a chip would ever be. Websites like opencores.org even sort of have what you’re talking about, but in general, logic design takes a lot of effort to be better than a general purpose chip that has had an insane amount of effort put into it. Also, no one wants to spend the effort the verify that the designs are actually right. Opencores is mostly full of half finished student projects, and has been as long as it’s existed.