If they don't want Ukraine to be part of NATO, then what's the answer? Russia takes Ukraine, and it becomes part of Russia, and then Russia borders Poland and Romania, so "we don't want Poland/Romania to be part of NATO" ... If this is the main concern, then the only solution for Russia is to take over all of mainland Europe. Estonia, Latvia etc have been in NATO for years, and it may have been a kick in the Baltics for Russia, but why would Ukraine be the concern?
This is exactly their goal. They are trying to recreate Soviet Union by increasing their influence over Central Europe and weakening their Western neighbors. They're building Nord Stream for that exact purpose. Before Nord Stream they only had "yamal", which they used to transfer gas to Germany through Poland, but that did not allow them to cut supplies to Poland without doing the same to Germany. Now they can do it and they are doing it. Last time I checked Poland was forced to getting their gas straight from Katar because Russia upped the prices on them so much that it was cheaper to send ships to another continent.
Do you know how you can recognize a country scared or already involved in an armed conflict? By conscription. Countries who still have it must have a need for it, because statistics have shown that conscripted armies are not as well equipped, trained and more expensive than volunteers. Most countries no longer have a need for conscription, but it still exists in North and South Korea, Israel... and Ukraine (which even requires women to register), Lithuania, Belarus and of course in Russia. Eastern Europe is like a big pot that's about to boil over.