Spoilers ahead.
Rewatching the original charmed and the 5th series is by far the best the first 3 with Prue were too serious, 4 was better, but the 5th series has some of the best episodes.
Phoebe becoming a mermaid, the one where they play out the fairy tales, the titans, Wyatt being born, Cole being vanquished,the leprechauns and more.
Whilst I can't remember all of the rest of the seasons as its been years I feel like it starts getting serious again with Wyatt being evil and Chris, Leo and Pipers issues with the highlight later on being the magic school.
But it is a bit annoying Phoebe never has premonitions anymore, Piper doesn't freeze time all the vanquished are potions, a spell or piper blowing them up.