alt Hacker News26k is a lot of transistors for an embedded MCU.
You'd be excluding many small CPUs which exist within other chips running very specialized code.
As profiles mandate these instructions anyway, there's no good reason to complicate the most basic RISC-V possible.
RISC-V is the ISA for everything, from the smallest such CPUs to supercomputers.
What MCUs are you thinking of?
To the best of my knowledge (and Google-fu), 26K really isn't a lot of transistors for an embedded MCU - at least not a fully-featured 32-bit one comparable to a minimal RISC-V core. An ARM Cortex M0, which is pretty much the smallest thing out there, is around 10K gates => around 40K transistors. This is also around the same size as a minimal RISC-V core AFAICT.
The ARM core has a shifter, though.