Technical characteristics like Android making it hard or impossible for third-party app stores to auto-update, as well as restrictive agreements with phone manufacturers and carriers are pretty damning. Google deserves to lose based on that, however,

their devices sometimes warn that the “file might be harmful” and require settings to be changed to allow “unknown” apps

Chrome on Windows warns that a .exe download might be harmful. Chrome on Linux warns that a .deb download might be harmful. We have a long history of malware using drive-by downloads or trying to pose as non-executable file types as evidence that these features are in the user's interests. At most, some rewording of "unknown" sources might be in order.