most microcontroller ISAs are just not designed with compilation in mind
This is true, but the AVR's architecture was specifically designed to be friendly to C. That was one of the reasons I became interested in it: after years of programming HC11s and HC05's in assembly, I had had enough :-)
For me code size has almost never been an issue (and only then when I needed to add a bunch of features without changing the hardware): the MCU memories are getting bigger all the time.
This is true, but the AVR's architecture was specifically designed to be friendly to C. That was one of the reasons I became interested in it: after years of programming HC11s and HC05's in assembly, I had had enough :-)
For me code size has almost never been an issue (and only then when I needed to add a bunch of features without changing the hardware): the MCU memories are getting bigger all the time.