To be fair to Mail.Ru, I believe maps.me is one product which became better when owned by them:

* they dropped paid version in dec 2014 (with all "pro" features, like bookmarks, being merged into free version)

* they opensourced it in 2015

* they added some OSM-editing capabilities in 2016

* they added bike navigation

I can't say how much of it is thanks to Mail.Ru, and how much - thanks to original developers, but it looks like the app was improving.

Note that in November 2020 it was sold to a new owners, - and after that, I believe, jumped down.