When doing paid marketing you need to track users as hard as you can otherwise you have no clue which ads work and which don’t, what are profit margins etc.

With GA, google uses cookies, fingerprinting and all other possible options to track correct attribution from various channels.

So even with ad blockers you can get a pretty accurate picture. It is also tightly integrated with google ads.

Plausible can tell you what users do inside your app. But honestly this is so basic you can pretty much build same functionality with a few sql queries.