I've found that you get what you pay for in the App Store (although my experience describes the Play Store).
The first mobile app I ever installed in 2015 was for-pay. I believe it was actually $14.95. It was worth every penny, because I'd used that website every day for years already. I was extremely eager to get the mobile app. It was a serialized podcast of sorts, and so having the app meant that I would have offline access to the podcast at the times of day (multiple) when I needed to use it.
I've purchased probably 3 or 4 apps, average price $10. And I was always happy to pay for the ones where I did, especially a fitness app where I gained little functionality but was able to support an indie programmer who'd made a really great offline-capable app.
In a few cases, I downloaded some free games, which I made sure interoperated with iOS so that my friend could play competitively. These games were sleazy, nasty, ad-infested, and probably Mafia owned or something. I needed a shower every time I played those games because, gosh, the things we did to earn coins were unspeakable. I happily uninstalled those games and I've never gamed again on mobile.
The apps I haven't paid for come in a few categories: indispensable utilities (password manager), preloaded brand apps (Android/Google properties), and paid services (my bank, my transportation, etc.)
So I don't really dabble much in free apps at all, because "free" means "ad-supported" or "freemium" or "spammers" and I just have no truck with that. You get what you pay for, and my phone doesn't have the space to be given over to fly-by-nights.