I'm unreasonably excited about Firefox OS. Android really isn't open enough for my taste, and my trust of Google has diminished over the years, as they've encroached on more and more of the web and my data on that web. Apple has always been awful for the open web. And I'd rather write JavaScript and HTML than Java.
Android's open enough for me, but what I find unhappy is that Google seems intent on tricking people into revealing more and more information. It often reminds me to turn on history tracking, despite having said no many times. Every time I use the Play store, it tries to get me to enter a phone number. The way it does this is by popping up a dialog, with no buttons except continue . It makes it look like you MUST do…
Try F-Droid, a repository of FOSS apps with a focus on user confidentiality. They offer some security assurance by building and signing the apps from the orginal source, and offer nice functionality such as automatic updates (which you can disable, of course). Their store and related app is a fork of Aptoide. I often can find good solutions on F-Droid, but the repository is small.