Crimea is a special situation. I won't reiterate its complex history here since there is plenty of written here, but I'd like to point out that one could have a view where Crimea is Russian and yet decry the invasion of Ukraine as illegitimate.
If anything for practical reasons: only 7% of its population is Ukrainian. It would be very a source of continuous ethnic tensions.
Hard Russian nationalism is much more than that
Such people claim that the entirety of Ukraine is just Russia and they mock them for otherwise being Polish. This narrative is an explicit outcome of an Imperial mindset