I've learned x86 16-bit assembly originally, and I find that most of that knowledge is still applicable when looking at assembly listings while debugging C/C++ today (which is the most likely area where one might have to deal with it in production these days; few people get to write asm from scratch).

For x86, at least, I wouldn't even say that it was less complex. Segmented memory alone is a huge complication, and then on top of that there was all the legacy CISC stuff like the BCD helpers or ENTER/LEAVE; x64 is comparatively streamlined.