DeX is not a fork. It is a UI layer on the phone that activates when you connect to a USB-C display. There is no difference between doing something on your phone and on DeX.
I wonder what you consider serious work then, because as a developer I think Visual Studio is the most "serious" developer environment there is, and I'd take it over any linux or Mac based setup.
Think about it like this: Would you manage a fortune in crypto on Windows? I wouldn't, because I just wouldn't even trust my environment at first. And for Visual Studio, I would solely run it in a firewalled VM.
MS employees have access to a lot of your work/data/fingerprints which makes it insecure by default. There is also serious privacy concerns, basic one would be that telemetry sends all HWID of devices by default, so if you share a USB stick with a friend, you two are automatically correlated in MS database, not really my cup of tea.
Not a big fan of an OS asking for an ID indirectly (via mandatory phone number) as well, mandatory MS account at install time (except if you tamper with the ISO, yeah sure)