That is odd- Have you tried:

• Where To
• All Pois

On my units, this is how you find POI's built into the maps - any maps - including OSM

As far as having a slow device, I can't say I agree- For me, it is no fun sitting on a cooking engine or under the rain at standstill in an unknown town (which is where Turn-by-Turn is really appreciated) waiting for directions due to the receiver/processor not being good enough in built up (concrete and steel) or poor signal areas.

I enjoy my GPS & Glonass enabled units- for they really make a difference especially when routing and taking a wrong turn- Maybe Garmin will add Beidou to the next generation- hopefully by the time China will open its borders without travel restrictions ( yes, I know- it is a long shot! )

I also used and compared many android nav apps and the one I kept is the free app called MapFactor Navigator but it is not as accurate nor as responsive as my bespoke satnavs- I also find that my smartphone also heats up a great deal ( no brands mentioned!)- The maps rotate to direction of travel and a host more of useful features too.

If without any other electronic nav aid, it does work better than those others I have tried, keeps OSM maps updated and stored either in your phones' memory or in the sd card- you chose. It does not replace a bespoke sat.nav unit imho.
As a backup, (or main unit) although the smaller screen makes it harder to read when moving along- I recommend the 64 series and in particular the ST as it offers the largest available memory capability ( at the moment!) -