Please don't. It's getting rather boring to see the baseless conspiracy theories that show up whenever an article is posted about gtk, gnome or systemd. Apparently they're trying to embrace extend extinguish their own business now?
Would you create a new open-source desktop application using gtk4? Would you want to package and maintain systemd/pulse/etc?
Also: why are you responding to all the critical comments in the thread, and writing dismissive replies?
Personally I would rather make a new toolkit, but it takes many years and many contributors to make a decent one. GUI toolkits are a complex business. Don't discount the amount of work that was already done on GTK or Qt, there are some serious lessons you can learn from those codebases.