Sure, Google is easier. The question was about what's acceptable, not what's easy or difficult.
The ease-of-use-is-all people can go sit in the "we don't care about open source" corner I guess.
The original article says that you _do_ have to use Google's Gmail if you want sensible functionality from the built in apps. You can use other providers, but things which should work don't work with them. My question still stands: why is that acceptable?
It's good that I can fork it.
In other words, I can turn a Google-requiring phone into an equivalently functional non-Google-requiring phone with some effort.
That is than Microsoft and Windows. But worse than something which works out of the box with other providers of identical online services.
Whether that is a real issue, or just ideology, depends on whether it stays that way, or if Android (the one from Google) interoperates well with other services.
Having to fork isn't an insurmountable barrier for a few individual users wanting to do neat things, but it is rather anticompetitive to service providers, since most users won't use a fork as long as the Google-requiring version is good enough.