Fair enough, but if Russia launched a punitive raid (went in, killed a bunch of Ukrainians, destroyed a bunch of stuff, then left), European stability would not be seriously threatened (because some Europeans want to believe that. Heck, there are Europeans who would agree with Putin after the fact that it had never even happened. The EU and NATO would send sternly-worded letters telling Putin how angry they are at him, and then the Eu would get back to what they have been doing.
Even if Putin were to invade and grab the aqueduct and dig in, Europe would be angry, but would do little. And the French and Germans would sit at the table and take Russia's side when Putin told the Ukrainians "We only did this because you have cut off water supplies to Crimea. It was a humanitarian action seizing the aqueduct." France and German would sit next to Putin and agree, saying, "Yes, you see how evil the Ukrainian water embargo is? Putin had to do this."
Now, on the other hand, if Russia launched an invasion and attempted to annex the entire country, that would be a different kettle of fish. First, that would threaten European stability, and Europeans would react firmly, by bolstering NATO members in Eastern Europe. The U.S. would as react strongly as well. And the Ukrainians themselves would launch a partisan fight like the Russians have not seen since the end of the Second World War. There is no way the Russians could hold that much territory (603,628 square kilometres).
I agree, Biden has handled this well to date. The jury is still out, however. Hopefully, I am right and this whole show was intended solely for domestic Russian consumption or for Ukrainian consumption, to draw away Ukrainian forces from the Donbas fight. Hopefully, that is all it ever was.