This concerns me. Under the current google model, as long as you have a play store compatible device, you get chrome webview updates through the play store, even if the device fw is eol.
If an app developer doesn't update their app, then you can have potentially vulnerable version of geckoview lying around. I hope a decoupling/webview-style update mechanism is eventually implemented, although I don't know how feasible that is (i'm an amateur android dev)
That said, I really do like the project. And, I use firefox as my personal browser, both on principle and because it's quality software.