You haven't seen any argument pro? You just have to read the technical arguments for Wayland, so either you don't like Wayland at all which would mean for you in fact there are no pros, or that should count as a pro in itself because that just how Wayland works. And on the other hand are these "many cons" which I think are highly exaggerated or even fictitious.
People come up with red herrings of things that will surely happen if we allow CSD while ignoring the facts that show that on other OSes they seem to be doing fine, no complete chaos of every app for himself and just drawing the decorations however they feel like (and examples that if an app really wants they can break the rules even on X, ie Chrome).
Apps built on top of the software made by their respective DEs won't even know anything changed, the core software in Gnome and KDE will take over the rendering of the decorations. So in one fell swoop a large quantity of apps will behave exactly as before.
Most other apps will not go through the trouble of rendering their own decoration either and will use some kind of system service/library for that (probably the same Gnome and KDE will be using).
So that only leaves us with those apps that decide to do their own rendering for some reason and that's when we have to remember that Linux/BSD are highly managed environments where apps that misbehave will probably get fixed or ignored.
And that's why I think CSD is not the end of the world.