The USA and UK already abandoned the Afghani people, feels like the once mighty US military really doesn't want to be in a shooting war against Russia. As someone living in Europe, I would also be wary of how it would escalate if NATO got involved.
Ditto Russia, UK, France, the other nuclear powers involved.
That being said, it’s a Rubicon all, will be reluctant to cross.
But in general I'd agree with you. On the other hand, who and literally what army would stop them?
Among several others, the United States military. Which, contrary to claims made elsewhere in this thread, is a pretty formidable defensive force. In fact, it even has aircraft carriers that can move under their own power.
There is not a single chance that Russia would have touch a NATO country, it's a war they could not win.
You would have to weigh how things would escalate if NATO got involved, vs how things would escalate if Russia found out NATO isn't actually a thing any country intends to honor.