Is there a core issue for that?

Hello @Anybody, we have submitted a request to Drupal to include "FormAlter as Plugin" in the core.

What makes form alters special over other alter hooks? why not a plugin for every hook?

We're getting into well trodden territory, such as proposals to improve the hook system generally, or implementing event dispatch/subscribers and weight/priority systems.

A recent example is #3366083: [META] Hooks via attributes on service methods (hux style).

And you have contrib solutions already which handle hooks/alters generally, such as Hook Event Dispatcher and Hux with priority/ordering systems. Each have their own way of doing dependency injection.

We're going to need a harder sell on why you want this and what makes your proposal unique.

Since nobody else but us seem to be interested in porting this module inside Drupal Core I'd say we can close this issue and leave things as they already are. Good luck with it