But the app is on android. A Google ecosystem, downloaded from the Google play store, displaying Google ads.

You're already Google's bitch before you download the app, so complaining about how a small, solo, full time developer is trying to monetise his creation using google ads just seems a little pedantic.

If you don't like the ads, pay for the service or don't use it at all. Personally I was happy to pay for the service, but for some reason people are still angry at the developer.