NATO had the local armies of the Baltics, Poland, Slovakia and so on the Russian border (by definition). NATO had the US forces in Germany reasonably close to the Russian border. NATO had the forces supporting the war in Afghanistan on Russians southern border None of that was, as far as anyone not informed about secret NATO planning, can tell geared against Russia. If your neighbor patrols his fence with a huge axe while your children are playing in the backyard, so, you would be worried I assume. Even if it was just to cut wood. Especially if you have bad history with that neighbor.
During the cold war, both NATO and the Warsaw pact conducted war games about invasions of the other side. War Games, because they needed something build their defensive strategies on. As it turned out, both sides, NATO and the Warsaw Pact, never had any real invasions plans for Europe, instead both side focused purely on defense against such an invasion. Turns out that this fear of the other side never died.
Since all that lies in the past, the question where we (as in the West) draws the line. NATO, and the US, kept a ton of unresolved territorial disputes in check since the end of the cold war. Most of those conflicts have the potential to turn really, really bad. If Russia gets away with their attack on Ukraine, others will, potentially rightly so, think they can do the same. And then the World-as-we-know-it might pretty much just end. Well, it might as well if NATO goes to war with Russia over Ukraine as well. Only bad choices it seems.
I see this tendency within many, if not most countries that have seen a decline in national power over some period, and were nationalists wanted to "Make <their country> Great Again".
Examples: - Germany under Hitler - Italy under Mussolini - France after WW2, when they were quite nationalistic for decades, and certainly did NOT like that English had become the "Lingua Franca" - Britain under Margaret Thatcher - Russian under Putin - MAGA - And most important of all: China under Xi Jinping
Some of these movements were relatively harmless, some were (and are) very dangerous
When I look long term, I cannot wonder how Russia will ever leave Crimea. Does that mean that Russia is the next Iran with "forever" sanctions? I cannot see another story, unless Putin leaves and the next leader is more centrist, like Medvedev.
The change is not in politics - for decades post-Soviet Russia wasn't worrying about NATO. Actually, no - even the point that Russia is afraid isn't correct - it's Putin who's afraid. NATO problem doesn't really exists.
Russian grand strategy is defensive. Their primary threat is a large-scale invasion. It happened once in the 19th century and at least twice in the 20th century. Maybe three times if you count Russian Civil War.
To counter the threat of a potential invasion, Russia tries to maintain a buffer zone of friends, puppets, and occupied territories. This is a continuous process, as politics change. Today's friends may be tomorrow's enemies, revolutions may overthrow puppets, and the costs of military occupation may prove too high. Russia fights wars and organizes coups to maintain the buffer zone. The rights of their neighbors don't matter to them when national security is at stake.
Russia fears NATO, because NATO has the capability to project power. They fear that NATO could be the next invader. The fact that NATO has no intention of doing so is irrelevant to them, because politics change. It's the military capabilities they are afraid of.
If there is going to be a change, it must come from inside. Russia must stop being afraid and become a member of the international community connected by trade. There was a chance of that in the 80s and 90s, but the chance was lost. Another chance may come after Putin, or the next leader and the next regime could be more of the same.