The Ukraine border area is where the USSR almost lost to the Nazis. It is an exposed jugular. A NATO base in Mariupol could cut them off from their black sea fleet/only warm water ports and their oil fields in the caucausus like the Nazis tried to.
You dont have to be a military analyst to see that Finland and Swedens membership is less threatening than ukraine.
Scaring Finland into joining NATO after their long held policy of neutrality was an incredibly counterproductive strategy for Moscow.
As said above, all nations sorrounding Russia that have joined NATO, have done so because they were and are afraid of Russia.
Russia has been saying "if Finland joins NATO, there will be consequences" since forever. When Finland actually joins Russia says "yeah no problem it's not really a threat". This is to not lose face, _obviously_, but all these parrots all of a sudden go "oh yeah no problem, you don't have to be a military analyst to see it's not a threat". They're just parrots.
Right. It absolutely is. Just nowhere near as threatening as Ukraine-with-donbas-and-crimea-and-most-of-its-coast joining NATO.
Theyll probably be more comfortablen with Ukraine joining NATO either if they turn it into a rump state with limited access to the coast and no control over the russian speaking heartland.