We are not comparing Smalltalk JITs to Javascript JITs.
The whole point of this conversation is CPython refusing to add one, and the lame excuses regarding its dynamic capabilities, when more dynamic languages have had a JIT for decades.
Second, my question was about the possibility that Smalltalk and others were unbearably slow without JIT, so JIT was not a matter of choice for them. I'm not aware of Smalltalk implementations that don't have JIT, so it would be easier to compare Smalltalk with another well-optimized JIT implementation instead---in this case JS.
My thesis work was on AOT JS compilation, in it I refer to a bunch of experimental Python runtimes, Self,etc and the main issues in all these papers were basically the of same kind.
Heck, even PyPy exists and iirc when it comes to the core language is almost entirely compatible (except for code that relies on ref-counting semantics but that code should apparently big fixed anyhow).
https://www.pypy.org/compat.html
The real summary is: CPython is a turd in many ways, the old C api holds it back and the community hasn't put the effort into using cross-implementation compatible C-bindings instead making PyPy or others a second class citizen.
Yet, not only are they in the genesis of JIT compiler research, their JITs are quite good, and their results went directly into JavaScript JITs research.