Swift is pretty next level compared to Rust. Rust does seem like a fairly constant level of slow and linearly slows down as the project gets larger. Swift tends to have huge degradations on seemingly innocent changes that make the type inference go off the rails. Although at least if you spend the time to track these down you can fix the worst offenders.

When doing UI things, a common workflow is to have code and the app side-by-side, make a small tweak in the code, recompile/hot-reload, look at he result, repeat. A long compile time makes workflow a pain.

In general, you're right. But there are at least 2 times where they're absolutely vital- anytime you're dealing with a UI and data exploration in data science (since you make a lot of frequent, small changes in the goal of fine tuning something.) Everything else, best practices has good testing and partial compilations to make it moot. There's probably some other contexts that make it valuable, but I've never had to deal with those.

It seems something like that already exists:

https://skip.tools/blog/scrumskipper

I mostly work with flutter but Skip looks pretty cool.

There probably won't be a cross-platform UI layer and many Apple frameworks won't work, although apparently the Foundation Swift rewrite already works. For a lot of companies though, simply being able to share business logic will be a big plus. At my current company we have a lot of talented Swift people and existing code written in the language so being able to share anything would be a huge advantage.

I'm biased but I personnaly find the language really productive to work with, runs fast enough for my needs and let's me target more and more platforms.