The problem for Russia was a complete lack of attention - they just considered it another guy's problem. And it was indeed another guys' problem, until Russia started a war with an industrial nation that didn't have any other choice...but had lots of advisors, who dealt with this exact problem firsthand.You are going down the rabbit hole a little.
Drones are giving the Russians a headache because they don’t have the right tools in sufficient numbers for the job sure, but also because geography and political reality is really not their friend in Ukraine and the Black Sea.
The problem for PLA here is that PLAN almost equally considered it until recently ... anothers' guy's problem. But PLA enemies are industrial nations, which have advisors...you see the pattern. I.e. I think it's a given at this point that drone warfare will be tried against China. Moreover, given how EU and Ukraine develop gray area attacks (surely won't backfire against a group of nations without global presence), this threat can turn real against Chinese shipping sooner than even actual war can start.
Like, for example, how much COIN/C-UAS gun mounts do PLA ships have? They do, in fact, have some (H/PJ-17 on 056(A)), but those apparently weren't terribly successful, as half the production run switched to a manual 14.5 MG instead.
Since then, nothing, assumption (much like Russia tbh) apparently is that "we already have 30mm at home".
Yes, i agree that maybe I'm overly impressed by what's happening. But this isn't just me being impressed; decision-makers are sold on that, too, even if they're desperate/incopetent and are absolutely getting fooled (Gulf contracts with Ukraine).
But fools or not, money and spread come to the issue.