I have not read really any negative reviews, a lot are just saying chapter one is better.
It: Chapter Two First Reactions: Epic, Brutal, and “scary AF,” But Does It Stick the Landing? << Rotten Tomatoes – Movie and TV News
Ummm...
“The film is easily one of the biggest disappointments of the year.”
“It: Chapter Two doesn’t stick the landing.”
“It: Chapter Two can’t quite stick the landing nor live up to the high expectations set byChapter One. “
“It: Chapter Two has a rushed, clumsy first act and an odd lack of chemistry among the adult Losers.”
“A dull and bloated mess that spends too much time rehashing things from the first film.”
Having this many negative reviews after a private screening (which typically generates all positive reviews to build up hype) is not a good sign.