I don't know if the information being out of date matters in this case, the problems of OS version fragmentation still remain.

Android antipiracy measures are extremely brittle and rely on server-side verification, this has been circumvented by decompiling app archives, patching them and rebuilding them, which is entirely possible using apktool or your decompiler of choice. Frankly im surprised that the platform isnt crawling with malware.

I wouldn't deny that fragmentation is an issue, although from my (limited) personal experience the biggest issue has been designing for all the different screen sizes/resolutions and still having your app look okay.

And yes, any antipiracy mechanism can be circumvented. That said, 90+% of android users probably dont have the knowhow to grab the apk, decompile it, and remove the server side check. And I'm not sure on this last bit, but I know at least in the US some carriers (ATT) disable installing apps that aren't from the appstore. I haven't read about the details of the antipiracy mechanism, so I can't really say more than that.

Also, its unclear to me if you're linking the fact that theyre so easily decompiled/cracked and that you're surprised it isnt crawling with malware.

Another point is that most Linux distributions have way more than 60% free apps in their repositories.