I think it's a little unreasonable to point blame at a group of people who largely built extensions on their own time, with no expectation of any form of compensation. It's entirely reasonable to decide you don't feel like supporting an extension anymore, and a community to take the reins doesn't just magically appear.

And regardless, there are still a lot of things that the old extensions API let you did that you simply cannot do with WebExtensions.

Having said that, Mozilla did the best they could in this transition. You can always argue that they cut over too soon, and that they should have waited until WebExtensions was a little more mature and covered more use cases, but the reality is you have to draw the line somewhere, and I'm sure they agonized for quite a long time over where that place would end up being. They also know a ton more about their users than any of us random HN commenters do and are way more qualified to make that decision than anyone here.