AngularJS is simplier and easy to use over Angular 2+.
Is there a way to use AngularJS in Ionic 3 and save the performances that Ionic team made, but with AngularJS instead of Angular 2+?
No.
Ionic 4 will extract the UI components of Ionic into their own package, @ionic/core, which could theoretically be used with AngularJS. But as AngularJS is pretty much EOL and unmaintained, I wouldn’t advise anyone to go that route.
That seems a bit steep opinion to me looking at the recent LTS statement on AngularJS, as can be found on the angular blog.
Nevertheless, if u r new to AngularJS, then it seems better to stay away
Fair enough. “Not developed any more and in pure maintenance mode” would have been better wording.