Ah, I think your clarification makes a lot more sense than your original phrasing, because Haskell's position is indeed that side effects are bad, not that effects are bad. The bad thing is "side", not "effects".
The suggestion is to use pure Haskell for the rules DSL only. The surrounding system that applies any side effects would presumably not be written in that language.
For one, Rust's "trait" system, which is a foundational part of the language that enables a lot of Rust's expressivity, is a limited imitation of Haskell's "type classes". Rust would be a very different language without it.
That's a bit of a strange statement. The Y combinator is an expression in λ calculus. It's like saying French is even more beautiful than the phrase "nouveau départ".
> Comic Sans is perfect for setting children’s activity timetables that are displayed in a school playground. It’s perhaps not as appropriate for announcing scientific breakthroughs.
> and why they are so absolutely lost when it comes to creating successful languages
They aren't lost—they're just more interested in actually good ideas than in popularity. Popular languages must appeal to all kinds of programmers with varying backgrounds, so they are heavily constrained. Your argument is basically that mathematicians don't know what they're doing because their most advanced theories aren't used by mechanical engineers.
Most of the functional programmers I know have a deeper understanding of OOP than the OOP programmers I know. For example, most of the OOP programmers I know do not understand covariance and contravariance (whereas just about every functional programmer I know has mastered them), even though those concepts frequently come up in the context of OOP. People who study programming language theory tend to gravitate toward the functional paradigm, but it's not because they don't understand OOP.
> Code has limited CPU available as well - if it tries to use too many cycles it quits with an error
That's a pretty strange failure mode. Usually you'd just throttle the sandboxed application (e.g., give it a CFS quota with a CPU cgroup) or give it a limited number of vCPUs.
This is actually the Z combinator, which is the eta expansion of the Y combinator. The Y combinator only works in languages with non-strict semantics, but JavaScript is call-by-value.