Would you use a personal aggregator that combined feeds from all those networks into one?
I use these services in different contexts.
When I'm relaxing and looking at Instagram, the last thing I want is a business article from LinkedIn or a political diatribe from Facebook.
In fact my primary problem with Facebook is that it tries to be everything to everyone.
Nilay Patel recently argued that Facebook is the new AOL, it's the portal of the 2010s. I think that is an apt description. I am using it yet also kind of just pining to drop it.
I also use it for groups and messaging. Somehow, Facebook groups are great. They're super simple, and they just work. The newsfeed on the other hand is completely broken.