Semi-related: Does anyone else feel like Ubuntu has lost a lot of its momentum over the past few years? I don't hear about things they're doing nearly as often anymore.
I think the "problem" is that Canonical has figured out - correctly - that all their worthwhile stuff needs to be done upstream of Ubuntu. Even their packagers know to try to get things in Debian first and to reduce diffs when they can. Unfortunately, that means that the unique Ubuntu secret sauce is all the weird stuff that no upstream wants, and if you're in no hurry to upgrade, you may as well run Debian.
This is pretty good for the world but I worry about the sustainability of Canonical as a company. I'm worried they'll end up like Mozilla - senior management finally realizes that doing excellent technical work in upstream communities isn't a net positive for their bottom line and has no idea how to remediate that other than layoffs.