Batman Returns is quite possibly my favourite superhero movie overall, at least from a spectacle standpoint, but, despite the throwaway mention of Vicky Vale and using the same Batmobile with only minimal modifications from '89,
Batman Returns is so over-the-top surreal that I have trouble even thinking it's in the same universe as the first Burton
Batman movie, which was already a bit surreal but not nearly to the same extent as
Returns.
I think for a long time the official Warner Bros. answer was "eh, whatever, sure", as though there was never any clear definitive answer and there is much online fan debate on whether they are all connected or whether the Joel Schumacher films different universes where Alfred and Commissioner Gordon just coincidentally happen to look exactly like their Burton/Keaton-verse counterparts.
But now the Joel Schumacher (RIP) movies will officially no longer count as Burton/Keaton-verse canon.