Who is to say that it isn't working as intended in building a higher wall around their ad garden? There should be a way for them to accept mail from self hosted users, or even provide some sort of testing tools (perhaps validated by credit card some type of bar to increase accountability? At least an RBL or something) for those who do, but nope.
Or more simple still, it's a hard problem to solve and when there's billions of emails flowing through the pipeline every hour small mistakes can look big to individual users.
"Never attribute to malice that which is adequately explained by stupidity", except for the "promotions tab", that was clear malice to increase their ads revenue.
I don't think they're bad, it feels more like they hit the 80/20 point and move on to something else. In the case of spam detection, whatever worked ten years ago set and forget without anyone quality assuring it as things evolve.
