I manage at a client an application which is the actual leader (most top right and by far) in Gartner magic quadrant for its category, and for years, I have never seen a product this bad, where the implementors and supports are clueless of their own product. And obviously it's buggy as hell.
The people who make the decisions don't use the product. That's almost always the root cause of this stuff. I worked on a system for my state - another vendor came in and 'took over' all the functionality my system handled. Supposedly. 7 years later, my system powers the exception to the mandate to 'use system X', because... they refuse to provide the functionality that they sold the state. Contractually, "we provide feature ABC", but the reality is.. they don't. I even provided them our code to use - it was paid for with public money, they should just integrate it and then sell it to other people to make their product better. They can't even be bothered to take the code and integrate it... they prefer to continually lie and say "we provide feature ABC" when... they don't. It's beyond insane. A large majority of the people on the ground know it's bad/lacking/broken, but ... they have 0 voice in the matter.
You would probably be depressed if you knew who our customers were, and how technologically unsophisticated they are.