I think Kubuntu would benefit by disabling the Splash Screen by default and also I think KDE Plasma should do it as well. The Splash Screen is rather dated and doesn't really accomplish much these days other than make the booting process take longer. I disable the Splash Screen on my own system immediately upon install because that way it lets me get to my desktop much faster on boot. Yes, things are still loading as I start to use the system but that is a normal expectation by users so there's no real issue there in my opinion. The Splash Screen effect just makes the user wait longer to use their system.
In my testing, the Splash Screen effect makes the boot process take an additional 10 seconds - 30 seconds, depending on the hardware, for no apparent benefit that I see.