Except that there is no "they". Unlike with Windows or macOS there is no Microsoft or Apple to make decisions for the whole "ecosystem". There are distro vendors, but they're more like app stores shipping pre-configured pieces (including pieces that we consider to be core OS functionalities). And there are a lot of them, so lack of consensus is not surprising. And then many vendors offer options to install this-and-that, so it's up to users to decide what exactly they build on their machines...
Given that there is no such thing as just "Linux desktop" (I mean, my setup can be completely different from another persons' one), it's hard to say whenever it's ahead or behind, unless every component option is known to be such.
