One thing I was surprised not to see was a mention of their Swift 2 to 3 migration, which was terrible in my experience working on apps that were nowhere near the complexity of Uber.

Apple should have never pushed Swift as hard as it did at the time. Between the constant API changes and issues like requiring dynamic framework linkage and copying the whole runtime into every app, it was absolutely not production ready.

It was a lot of work, but we had enough staff to make it someones job for half a year or a quarter, depending on how bad the migration is. With big codebases there are other issues that pop up with every new major Xcode release that we have to migrate, mitigate or fix. For example we are still at xcode 11 because of various bugs in xcode 12. Doing the migration was annoying, but it was not much compared to all the other issues, because the fixes were tractable.

That's why I call idioms idiots. If you have to learn idioms, it's an idiotic thing.

There is no language where full expression is possible without use of idioms that don't have direct translations in every other language.

What do you propose as an alternative?