There are several big web portals - Poki, Crazy Games and Yandex Games and they support ads monetization. You can use whatever you want - phaser, threejs, babylonjs or Unity with web export. The key factor here is how many users you will be able to convert into players because web is huge.

Gamedev is long term investment for me. Especially with web game dev. You can launch a new game every 3 months and after 2years you will have a good income. I suppose it is different for steam/mobile games

Cool! I think I had 2500 ccu max for my game on poki, so push harder! 😄