I like Friends, but have seen every episode so many times that I am 'done' with it now!
I think all of the characters were flawed, that was part of the comedy. However, I loathed Joey - the implication with him, it seems, was that he could get away with being sexist, immature, lecherous and so on because he was (a) supposedly, nice looking and (b) unutterably stupid. I cringed every time he came out with the 'how you doing' line.
I always felt sorry for poor Chandler because he had experienced an unhappy childhood that led him to be hopeless at relationships and defensively witty, sarcastic and so on.
Ross was just a spoiled man child with his absurd interest in dinosaurs (his job was really just an extension of his childhood obsession - the joke being that he never really grew up. He is possessive, jealous, pompous and so on - he's also willing for his best friend (Chandler) to take the rap for his teenage drug use.
I agree with the fat shaming. Actually, I always thought 'fat' Monica was more attractive than her excessive skinniness after the character lost weight. I believe the actress suffered from bulimia, so it's ironic that she plays someone with issues around control and weight gain.
My least favourite character was Phoebe and her awful singing. She had the best lines, but there was something about her that I don't think appealed to British humour - the kooky hippy character became tiresome.