Regarding Carrie and Big however, I'm not sure why it was painted as some great love story?
First season - she wanted more than he was willing to give and it became toxic.
Second season - same as first, only this time around Big should have been factoring her in more, especially as he agreed to get back together, but didn't tell her he might need to move to Paris for maybe a year.
Third season - comes back from Paris having married a woman in her 20s. Goads Carrie at the furniture show and the hotel she was working from. Have an affair.
Forth season - are "friends" yet neither considers Aidens feelings with the country house/general contact with eachother. Big moves to Napa and again, wasn't going to tell Carrie he was moving.
Fifth season - Carrie uses her column to make a book which both romanticised their "love affair" as well as shows it in its full toxic time line. Carrie basically gives Big a get out of jail free card for how he treated her so she could get a shag, even though Big had finally seen how he had been to her and that would have been a great opportunity to have a good conversation and gain closure with him finally admitting that it was partly his fault too.
Sixth season - Big only appears when again when Carrie is moving on with her life (that's not to say the Russian was good.)
In-between all the big storylines, there's the times Big was a jealous prick such as the jazz guy episode! He always mocked her dating life and actually told her "baby you're not the marrying kind..."
Toxic all the way through.