chatting with other mobile devs, not doing VNs but puzzle, arcade, etc. They are all experiencing crazy drop of traffic sales and thinking about quitting. Sucks, for me was always a side revenue but for many people was main source of income 
I think has become very competitive, most mobile games are F2P/loot boxes and such, so they can afford to pay $$$ to "acquire users". But pay-once games like mine are heavily penalized by this system