My impression in the 90s is that most people talking about embedded were talking about microcontrollers or very limited microprocessors.

My counterpoints would be e.g. QNX and vxWorks, famous embedded OSes, both being active in the 90s (roots go to the 80s, but in both cases afaik they really came into being and found a market in the 90s). Plenty 90s embedded hardware with x86 CPUs in it.

What's probably different today is that you have more options also on MCUs (not just assembly and maybe C), because MCUs have grown.