1) top heavy, because all the hardware is on the screen portion, so it's difficult to balance and use it on your lap
2) lack of processing power due to the form factor and thermal limitations
3) lack of touch friendly windows apps that can make it truly useful as a tablet
1 probably can't be helped, but 2 and 3 should definitely be better now especially since Apple silicon and iOS exist, if they choose to make something like this...
#2 is subjective and depends on your use-case. I find that for mine (circuit design, PDF markup, email/web, low-requirements mechanical CAD, casual gaming) it's totally fine.
#3 is very real. I don't use the Surface Pro as a pure tablet almost ever. The only exception is if I'm stuck on a plane and there's no room for the keyboard and all I'm doing is reading.
I really wish the keyboard could talk wirelessly back to the tablet so that I could put the keyboard behind the screen and still type on it every now and then when I'm primarily drawing with the computer.
Apple has the technical capability to make a Macbook that is separable. The screen comes off and makes an iPad.
It also has the technical capability to make a bi-modal OS.
OSX with a HW toggle switch that allows OSX/iPadOS modes. The switch could be nearly seamless. The unlimited freedom OSX mode is an overlay FS on the iPadOS mode. Change anything you want, run anything you want and when you flip the switch, the OSX apps are frozen to disk, the overlayfs unmounted, and you still have any iPadOS apps running. Flip it back, and the OSX world resumes as it was.
But you can't have this product, because the marketers at Apple know that you would never buy an iPad again if you had this.