I use the gallery. It is simply a foldered list of my images - sorted by most recent. It doesn't try to upsell me anything. It doesn't have a tonne of features I'll never use.
It is much faster than my phone manufacturer's gallery.
I've used the audio recorder. Other than the permission to use the microphone, it doesn't use any other permission. It doesn't even ask for general filesystem permissions, and assumes you are savvy enough to know how to use the standard Share functionality to get the files where you want.
The app does exactly what it says (records audio) and doesn't phone home, try to integrate with any services, collect any information about you. It just works.
If that type of thing is important to you, and you have a need for the functionality provided by one of the tools, there's your use case.
I use a few of these - simple file manager, simple gallery - on (my wife's) devices which are encumbered by custom Android shells (Samsung and Sony to give a few examples) which make it harder than necessary to perform certain tasks. They are complementary to whatever is installed on these devices, they're not in the way, they're free (from F-Droid) and I don't really care about that orange theme since I only use them occasionally. If you have an AOSP-derived distribution like LineageOS installed there is not much need for this type of app but for those who are stuck with custom Android shells like Samsung's Touchwiz and Sony's Xperia some of these 'simple' apps can come in handy.
They are on F-Droid, which is an alternative Android app repo for open source apps (in fact I think the team builds the apps from source themselves). In addition to their requirements, they audit apps [1] and have been audited themselves [2]. The repo also lists any concerns (eg if the app has tracking) in the description, though the vast majority have no issues. And afaik there has not been a single case of malware (even though similarly sized repos have had them [1]). F-Droid is by far the best place to get FOSS privacy-respecting apps.
However due to the stringent requirements, you can imagine that the selection is smaller. For simple everyday things like a phone dialer, contacts app, gallery app, calendar, etc, Simple Mobile Tools will show up near the top of the list on F-Droid. A lot of alternatives are just old and unmaintained. Simple Mobile Tools gets the job done and has a decent UI, so you can uninstall whatever sketchy bloatware your phone came with and use these instead.
TLDR: if you care about FOSS and privacy, these are often your best option.
