Be careful what you wish for. 
Once save is added tycoon-like games will have much higher retention than minigames.
About current situation I disagree that all tycoons are played only once. Non-linear ones can get 20%+ retention. All of these number are still pretty low, in mobile games space anything below 35% is considered bad.
Algorithm is far from being good but I don’t think focusing more on retention will improve it and probably will make it extra hard for new maps to get to Discover.
Other ways it could be improved:
- ratings (1-5 like in Roblox)
- quit rate (how many players quit the game after playing a map)
- item shop device use rate
- discover vs map code use rate