Google products like Reader tend to use internal APIs for storage, authentication, request routing, deployment, logging, builds/tests, etc. It can be a lot of work just to keep up with those internal changes.
The real problem for Reader was that it wasn't worth any engineering effort (because it only had a couple of million daily active users).
This mentality is entirely the reason why large corporations can never do anything apart from their core business, and why they always spend billions acquiring startups (which usually fail to integrate into their business). They just fundamentally are incapable of creating anything new, and when they somehow do it the incentives are so misaligned they shut it down and the only thing they get for their efforts is making the public rightfully hate them.
Google killing Reader was very shortsighted because they’ve hurt the open web in an effort to promote Google+. And it was all an effort to promote Google+, nothing more.
Reader was perfect the way it was and could have been left unmaintained. Don’t tell me that Google couldn’t spare an intern for the occasional fix.
And I don’t have any numbers however I’m willing to bet that Reader was, as a social network, far more popular and active than Google+ ever was.
Also such metrics don’t count the brand damage. I will never forgive Google for killing Reader and as a result I have rejected again and again Google’s products. Even at work I just convinced everyone that we must not depend on Google’s Firebase because we can’t trust Google.