GetX is the second most famous state management solution and exceptionally quickly developing in popularity. Is also the most controversial and evoking conflict in the Flutter developer community because many developers hate this package due to antipatterns, bad testability, or documentation, but many developers also love it due to its simplicity and very shortcode which you write so then you feel more productive.
Furthermore, there is a conversation between the creator of GetX and creators of other state management solutions (Bloc and Provider) which probably causes much hate in the Flutter community against GetX.