I feel like the Elementary folks have a lot of the right ideas about how to build a desktop OS and a third-party software ecosystem around it. (In particular: They have a HIG, and seem to make an effort to make their platform appealing for developers.) But it sounds like they struggle with execution in some ways:

https://www.dedoimedo.com/computers/elementary-0-4-loki-agai...

I haven't tried Elementary, but I've tried a lot of distros, and I always come back to Ubuntu because it comes the closest to just working. (It doesn't do as well as MacOS or Windows in the 'just working' department, in my experience (let the flames begin!), but it does pretty well, and better than any other Linux-based OS I've tried.)

And although reliable statistics seem to be hard to come by, my impression is that Ubuntu is the most popular Linux-based desktop OS by a pretty wide margin.