For me if I had to pick a good contender it would be the UK version of The Office.
I know many tend to debate how Ricky Gervais really fell off and how he repugnantly acts like a whiny centrist edgelord but me personally IMO I actually don’t think he was ever funny not even a little.
His big break through television was just so painful to sit through it’s so charismatically boring the characters are completely generic at best (notably Tim) or straight up insufferably unlikable at worst (especially the protagonist David FUCKING Brent) and most importantly the humour is just embarrassing.
Always seemed like The Thick Of It but without the nuisance tongue in cheek and charming satire.
Citizen Kane is generally considered the origin of the “innovative media that’s considered boring because everyone copied it so now it seems cliche” trope. It was a masterpiece when it came out, but it pioneered so much stuff that became commonplace. When a modern audience looks back at it, you just see the cliches, without realizing that they’re only cliches because they were endlessly repeated afterward.