Genuine question: what are you basing these 'trust' judgements on, especialy in the case of the Android apps? Open source, or something else?
Proprietary app stores are... nearly as much of an exact opposite I can think of, regardless of who sponsors them; Microsoft, Amazon, Google, or Apple, devs are putting apps there to get paid. Sometimes it's user data, sometimes it's "Free" with in-app purchases pushed by dark patterns, sometimes it's to push for consumer lock-in, and sometimes it's straight up malware, like most flashlight and cleaner apps on Google Play. Regardless, the incentives don't align, and that is what I'm on about when I use the word trust here.
People don't like it when a UX change is made by and for the company that just so happens to screw lots of users, or break or slow their usage. That's exceedingly rare on apps made by devs in the first category, and depressingly common for the latter group.
a) open source b) built by fdroid's CI from source without depending on external executable binaries.
https://f-droid.org/en/docs/Inclusion_Policy/
One of the reasons I trust F-Droid more than Apple's App Store and Google Play is that F-Droid prohibits proprietary ad and tracking libraries. F-Droid reviewers are also more technically proficient than Apple's App Store reviewers and less likely to err in judgment.
Most apps in the iOS App Store are chock full of spyware that reports on everything you do in the app. Many of the Apple system apps function the same way too (even with analytics disabled).
From a (my) relatively uninformed perspective, I'd have expected the opposite - that the iOS App store was more of a 'controlled' environment, and the Play store more like the wild west. But maybe this is just me believing Apple's marketing...
Both Android and iOS now do a fairly good job sandboxing the filesystem, but both cannot protect against advanced fingerprinting/data processing. Apple can outline acceptable data processing terms in the App Store, but that doesn't stop bad actors from taking data and processing it remotely. In Facebook and TikTok's case, this is almost certainly what's happening - and why the government is the only one capable of holding them in check.
The "alternative" is restricting the amount of entropy a user can generate to near-zero, which isn't really useful for app developers. Suffice to say it's an unsolved issue, even with a singular App Store.