Just because Nintendo, Sony, Microsoft are doing the same bad thing Apple is doing doesn't mean it's not a bad thing. Personally, I think game consoles should fall under the same type of scrutiny, but that's a different situation because, historically, game consoles have not been seen as general purpose computing devices. See for example the stupid DMCA jailbreaking rules that allow customers to jailbreak their phones, but not their game consoles. Why? Idk, I'm not a lawyer, but it probably has to do with lobbying.
Android's 85% market share is global, and a lot of those are low budget garbage which makes them less important for a lot of industries (particularly gaming). In the US, Android's market share is more like 50%, and while I obviously can't speak for every developer, I at least consider the US market to be my primary focus. Doing significant business in another country is more complicated than just localizing strings and clicking a checkbox on the developer console (unless your business is relatively simple, like a utility or a game)
And while Android does allow third-party stores to exist, they're at a significant disadvantage competitively. It is practically impossible for any store to compete against Google play with the current systems and barriers Google put in place (as proven by companies that have attempted it over the years). That is also clear "anti-competitive behavior". From the point-of-view of users, the situation is better. But from the perspective of developers, it's the same bullshit. You are not going to escape Google on Android and hope to have a successful business, unless maybe you can manufacture and sell your own hardware.
And regarding Steam, I too think that 30% is too much (especially because Valve are not entirely innocent of anti-competitive practices themselves). However, it's not the same situation because there currently are many realistic alternatives to Steam, both for gamers and for developers. The same can't be said about Android or iOS.