If my neighbours were surrounding me, digging up trenches and setting up gun nests, I’d want them to stop expanding too.

wrong analogy. a country simply joining nato does not mean it's actively preparing for war.

If NATO isn’t an offensive alliance meant to contain Russia, why did they refuse Russia’s entry in early 2000s, when there was no anti-west posture?

did it? it is an anti-russia organization, but a defensive one. no nato country invaded russia. russia chose to invade ukraine.

and so what if nato expands? none of them have an interest in invading russia.

so putin was never promised that nato would not expand. he has no right to complain about it.