The real problem wasn't "tying Google+ to everything"
The real problem was "tying the *name* Google+ to everything"
like they somehow thought that if they called 20 unrelated (and individually great) services "Google+", people would be tricked into they should use Service X just because they use Service Y.
Identity management for all google services? It would be insane not to have that. We'll call it "Google+"
A messaging platform for talking to friends and professionals alike? We'll call it "Google+"
A video conferencing app? Well, that's arguably part of messaging, which we're calling Google+, so it's also called Google+.
Want to share a photo? Me too. Google+ is great for that. No, no, not *that* Google+, the other Google+
Over time, each of these services have gotten their own name and branding and app and experience. But everyone still thinks "I hate Google+! It keeps asking me to join it every time I want to share a photo! I am not interested in a new Social Network!"