If transistors are made smaller, quantum physics applies and electrons can simply just go through shit. There is likely no way around this, although the "best" (ie smallest) transistor tech is still lab based (in other words a few years before it will be widely available). The future is multi-core and has been since about 2004, although most tech companies didn't accept this until the late 10s. Multicore processing is a mess for most programmers to deal with (and can't solve fundamentally hard problems) , bad coding practices are widely held onto, and people repeating Moore's law for the past 2 decades has damaged many programmers brains. Combine that with a silicon/transistor shortage (largely because of corporate weirdness, greed, and the fact that the process cannot be done "easily" on a smaller scale) with all that and you get the next stage of computing. Oh and on top of this a lot of companies/programmers view the current state as "good enough" so they don't care to do better.

TLDR: Physics and computer science have real world limits largely ignored in the past 2 decades, and those limits are being approached.