> don't you think they'd be using that capability against Ukraine?
No, and that's entirely the point.
Their non-use of their advanced weapons systems is as equally interesting a subject as their forward-deployment of expendable, less advanced systems.
The Russian military certainly have their inefficiencies - as all modern militaries do, including "our own" - but they also have capabilities that are going to be more important to use against NATO/USA, than Ukraine.
The Russian mindset appears to support the idea that World War Three is well and truly under way and has been since the West illegally invaded Iraq, in 2003. Ukraine is merely the latest in this conflagration that has been rendering 'lesser nations' asunder, for two decades already. The whole world has been watching not only American/NATO, but also Russian doctrine in play for decades.
So I guess the doctrine is, don't play your best hand first .. and reserve your big muscle for when you fight big muscle.
NATO is adding its muscle to Ukraine, no question. But I wouldn't expect to see Russian - or NATO - advanced weapons systems in use until there is actually direct, open conflict between Russia and NATO.
Only then would non-nuclear EMP's, and indeed tactical ("micro") nukes, and other such more 'advanced' weaponry end up on the battlefield, if there is even one after the first few hours of 'real war'.