None of this even attempts to address the problem of Google Play (the primary android app marketplace) being filled with malware. Every single app that’s being distributed through Google Play today already has a “verified” developer by the same criteria they’re applying system-wide. That malware can continue working as it already does without any changes.
This is exclusively about Google imposing control on all apps distributed through channels that otherwise used to be outside Google’s control.
Google’s claimed reasoning is that this control is a good thing and makes them be able to block apps made by malware developers in the same way they already do in Google Play, even for users who install apps from other sources. Critics disagree because Google forcibly taking personal information and money from all software developers and wielding the ability to remotely kill any app they don’t like for any reason have far wider consequences than protecting users from malware, and the proliferation of malware on Google Play shows how (in)effective Google’s measures against it are. Neither side believes or claims this can or will make Google Play any safer.
Mir is a pretty notable example. In 2013, around the same time development on Wayland sessions was picking up for the other desktops, Canonical decided to try doing their own incompatible thing and designed their own display server system to replace X for the then-upcoming version of their Unity desktop.
Ubuntu switched from Unity 7 to Gnome 3 before Unity 8 and Mir were ready, leaving both projects abandoned by Canonical and handed off to the community. Long after it had already lost what little relevance it had, Mir eventually was converted into a Wayland compositor.