Despite being terrible, the last time I checked, the experience in Xcode was somehow still meaningfully better than with the VSCode plugin

What don’t you like about the VSCode plugin?

For me it just spins forever and never manages to do any LSP things

If you haven’t tried recently I’d give it another go. A lot of work has gone in to the LSP this past year to stabilize it and improve performance.

Pretty similar to the Xcode experience, then

I find Xcode completion and especially doc lookup pretty good. It’s not as good as being able to jump straight into framework source code like with Android Studio but better than pretty much anything in VS Code in any language.

That is, as long as there’re no type errors in my code… once I get a little too creative in SwiftUI all bets are off.

I believe it still does at least for iOS, or it did last time I checked (for a Swift library I was writing).

Building Swift code for iOS without going through xcodebuild is sort of obnoxious but is possible. You do need to have a copy of Xcode installed regardless of programming language simply because the iOS SDKs aren't distributed separately.

Hence this announcement is great, since it seems to say they’re (going to?) support building GUI apps with SwiftPM and/or the newly open sourced build tool.

SwiftPM has always supported building GUI apps.