What tool do you use for collecting user data?

Idk if it's me, but things like Firebase Analytics seems so overcomplicated for what I need to do.

I just want to collect simple data about what users do with my app so I'm able to make wiser design choice. I just need to be able to answer simple questions such as:

• What number/percent of users use a specific functionality, so I know if it's profitable to spend more time on it
• If my app has to display a list of item, I want to know how many items my users has on average, and how many is the maximum our biggest user has, so I can make performance/UI adjustments according to it

What do you use for this kind of task?