To be honest, at the beginning I also used maps form Jolla, there were some third party apps but none of the were polished.
Maps wasn't really good, but the best at that time.

But nowadays, i don't miss it in any way. There are really brilliant third party apps which are much better than maps ever was:
Poor Maps
OSM Scout
and modrana are my favourites.
Together with OSM Scout Server there are not much wishes left for me. Why not just give it a try.