Having read and written assembly on a daily basis for years, I have to disagree entirely. The only simple thing about assembly is that it happens to map to machine code directly, but macros and quasi-instructions even make that iffy. There are so many idiosyncrasies in every ISA, so many ways in which the code you write has side effects. Assembly isn't just complex in practice, it's complex in concept.
If you want simplicity, you look at lisps; homoiconicity is perhaps the most elegant, simple concept known in computing. It may be more complex in practice (many more layers above the bare metal), but in concept it's simply beautiful.
