AppCode was unfortunately extremely limited. Lagged behind Swift versions. No editor for Storyboards/XIBs back when they were ubiquitous, and no preview for SwiftUI. Debugging app extensions or anything that isn't the standard "iOS app" was generally flaky or outright not supported.

There is a lot of interest as IntelliJ is a good IDE, but AppCode just wasn't reaching the bare minimum required to have me not use or worry about Xcode.