30 free levels is still too much. You need to drop it to about 10 levels, and then start charging. Level 10 is where you get a lot of people eager to keep playing, and the rate of abandonment doesn't drop, so to me, this is the best place to make them pay. If they won't pay at level 10, they won't pay at level 30.

And I think you are right, you are being nice. It's strange that you don't want to use standard monetization techniques, yet you complain when you don't make any money. It's sort of like the "nice guy" who gives everything to the hot chick in class, and then when he asks her out, he's shocked when she declines, saying that she wants to be friends.

There has to be a give-and-take between producer and consumer, and the best producers know how to balance that properly.

If you give your users a good experience, then they should pay to support your development costs. Saying you don't like pop-ups or you don't like ads is frankly nonsensical for someone who is trying to make money. There are ways to do both tastefully, and at this point, people realize that in-game ads are a necessity of life for a free product.