Actually, there's a (devil's advocate) argument for teaching assembly first. After all, TAOCP is all assembly for good reason. Many programmers who never learn any assembly language lack a kind of procedural literacy, as well as a mechanical sympathy, which are a big part of the craft of programming.

But, as you state, there are a lot of higher-level programming concepts you can't effectively learn in assembler (one imagines a bizarrely circuitous route around learning to build compilers in assembly (via Forth perhaps) in order to teach lexical scoping or similar).

Obviously I'm not suggesting that assembler is the best teaching language. I could also take your logic and use it to conclude that C++ is the best programming language to learn first because with C++ you can learn about the implications of heap corruption when improperly handling exceptions in constructors. C++ allows functional, procedural and OO and many more programming styles. It supports manual and automatic memory management. It can be used to teach high level and low level programming constructs. But I think we're all in agreement that C++ is not a good first language to learn despite (or because of) its versatility.

I think Python is a very accessible programming language that still has enough depth to go into a lot of interesting CS subjects. That Python doesn't have manual memory management or support for true multiple inheritance means that you can't teach those things effectively with Python, and I'm completely OK with that trade-off.