The team revealed Monday night the flag will stay in the rafters at Crypto.com Arena for the foreseeable future ... something that ain't exactly sitting right with plenty of fans of the storied NBA franchise.

After all, the team's won SEVENTEEN world championships -- and as you can hear in video from the pregame banner-raising ceremony prior to the contest against the Knicks, when L.A. officially hung the IST title keepsake, Lakers supporters didn't seem thrilled.

There was merely a smattering of applause ... and even LeBron James and his teammates didn't look all that pumped while watching the festivities from the court.

Of course, there were some who liked it, including Metta World Peace -- who told TMZ Sports last week he was definitely in favor of keeping the memento at the Lakers' home facility.

Several celebs in attendance at the game didn't seem to mind it much either ... Timothee Chalamet was all smiles in his courtside seat -- although his New York ballcap showed he probably could care less what L.A. does when it comes to decorating its arena.

Kevin Bacon, Dustin Hoffman, Mookie Betts and several other A-listers were there too ... and while it's not entirely clear what their stances were on the banner -- we take it they probably don't care much either way.