Computation is a rabbit hole, there is no end to its depth.

Comparing the definition of C++ to Haskell, one will see that there's orders of magnitude more incidental complexity in the former than the latter. Every professional Haskeller I've spoken to who previously did professional C++ has emphatically agreed.

Oh yes it is. I've done both for a long time (C++ since early 1990s, have known committee members, written a lang proposal, Haskell since '07).

The difference is that the C++ complexity is mostly from fitting abstraction into the legacy compat/efficiency constraints, while on Haskell it's learning more math/theory.