Google Maps (both app and web) and Here are out of competition, because they presumably are primarily data collecting tools, while navigating / displaying maps is their secondary function.
AFAICS Maps.me (https://maps.me/) falls in the same category, but an outdated Free Software version "MAPS.ME" (com.mapswithme.maps.libre) and a maintained fork "Maps" (com.github.axet.maps) are available at F-Droid.
So I took a look at "Maps".

Yes, its UI is simple and clean (too simple for me, but "parents compatible" in contrast to OSMand), but PureMaps definitely looks nicer and seems to be on par in functionalities, except for the "driving / public transport / cycling / walking" map modes. For these and some other functions "Maps" provides a couple of really good and some cool ideas for their UI design.

WRT comparing PureMaps with OSMand:
I fully agree that OSMand's vast and highly configurable feature set (in terms of functionality and visual appearance) is too complicated for beginners. And while I enjoy many of those features, I really depend on far less and dislike configuring a new OSMand installation (~ 20 minutes, and always missing something) a lot each time.

Thus trying to mimic OSMand or "Maps" is not a sensible goal per se, but certain functions and UI design elements of these apps are IMO worth to be evaluated, if something similar might be implemented in PureMaps.

I did not perform a proper check ever, it was just an impression I had using PureMaps (and predecessors) and OSMand every now and then in the last 1,5 years. You already provided reasons, why this may have changed.