The Linux Desktop isn't dead, it just never had mass market appeal.
There was a belief for a while that mass market appeal was required for the future of Linux on the desktop but over time it's become apparent that really isn't the case.
The number of people working on the Linux desktop would be fairly constant whether it has mass market adoption or not and in many ways lots of those developers simply don't care about mass market adoption (which brings with it problems of it's own).
I've used Linux as my primary desktop for 16-odd years and things have never been better from my POV as a developer who uses Linux as a development desktop.
There was a belief for a while that mass market appeal was required for the future of Linux on the desktop but over time it's become apparent that really isn't the case.
The number of people working on the Linux desktop would be fairly constant whether it has mass market adoption or not and in many ways lots of those developers simply don't care about mass market adoption (which brings with it problems of it's own).
I've used Linux as my primary desktop for 16-odd years and things have never been better from my POV as a developer who uses Linux as a development desktop.