You Sweds are strange!😉 Explain yourself?😀
Theres no way your telling me that Buffy is the same character in season one than she is in season 6 for example? And Willow has some of the best character development of anyone across the two shows.
Also the thing about Angel is that becoming the lead in his own show was a big reason why people now see the character as totally different than on Buffy which isn't quite the same as character development. And from S2 of Buffy onwards his character did start to change anyway.
Haha, of course Buffy isn't the same in season 6. She's gravely depressed in season 6. But depression rarely means character development, often it means regression, it is what comes after a depression that one should look to, the person coming out of all of that pain.
So let's look at
Buffy season 7, has her character developed? Nope! Not in my opinion. To me she has the emotional maturity of a blue berry scone. In fact, she has the mentality of Season 3 Buffy. She's even making the same mistakes in a new setting... having a judged relationship/friendsship with the vampire du jour after a tragedy between the two. Losing trust in Giles and shutting him out (as in after Helpless) And bumbling about high school pretending like she knows what she's doing.
You could argue I suppose that as the season goes on and she has to become "General Buffy" she grows... but does she really? Does she not just isolate herself from her friends? Seek comfort in romance that one could consider doomed? And act like a petty 17 year old once Faith comes to town? Does she behave better/take better care of Dawn... meh... she's not depressed anymore but as a parent, Buffy is a failure, Dawn continues to be overlooked and neglected, it's just that she's older now (SHE has matured) so it's not as obvious.
Have we not already seen all of these exact things, and the exact same emotional range? So how exactly has Buffy developed as a character I wonder? I just see her making the same mistakes, not really learning from them, and ending the season by acting not more maturely or wisely but majorly out of character (with the empowerment bit). Buffy in season 7 has for me regressed back into being a teenager.
Let's move on to
Willow.
Willow has a good arc of development between season 1-4, she's becoming a young woman, she's finding her sexuality and her talents and..... bam! Grinding halt during season 5-6, for these seasons Willow is exactly this; lesbian who does magic. That's her entire development. There's no internal development, only external. Willow shows clearly that she's an immature child throughout these seasons, who reacts according to her own pleasure principle and only exists in combination with a romantic partner.
E.g. distraught child Dawn, having just lost her mother, is placed in the care of Willow and Tara while Buffy deals with stuff. Said distraught child wants to magically make herself feel better. Tara explain this is not what magic is for/shouldn't be done. Immediate-satisfaction obsessed Willow however, if not literally, practically placed a book with presumably black magic - one that leads to it - into the hands of said child, without supervision, because she can't stand to see Dawn upset. She is well aware what these books contain, and regarldess if she thinks it's impossible for Dawn to reanimate the corpse of her mother, she should not be pleasing Dawn in this respect just to make herself feel better. But that's what Willow does. She has stopped growing as a character and just runs around reacting and waving her fingers at stuff she wants, takes and haves... including Tara as we will see later on.
But surely her addication arc shows growth... not really. It's just Willow again, acting according to her pleasure principle, wanting immediate satisfaction.
But surely her coming back from addiction arc shows growth? Meh... she takes a few stumbling steps... right back into the arms of her girlfriend! (Any addication cleansing program worth its salt will tell you to stay away from romantic entaglement for the first months/year of becoming clean so as not to replace one addiction with another.) Is this not what Willow does? Is this not why she can't grieve like a normal person when Tara dies?
Again, turning evil is kind of like depression, in and of itself it doesn't mean that the character is showing any signs of growth. It often points to the contrary. It's what happens after that you may look to for signs of growth.
So lets journey to season 7 and look at Willow. Has she grown? Well, it's rather understandable that at first she reverts back to a rather timid season 1-2 version of herself, but once she's more warm in her clothes and around her friends - is she showing any signs of development?
Again... meh. She's kind of the token witch by this point. What exactly does Willow do during this season, like at all? She's just kind of kept in the background until... dun dun dun... she gets another girlfriend. Clearly Joss and company don't think characters are interesting, or can have interesting storylines, unless they are in a relationship. Is this character development? Well "The Killer in Me" gives us a glimpse of this but it's hardly like this one episode is enough to fullfill a season's arc for a character, even if her girlfriend's tongue is pierced.
Then of course there's the spell at the end of the season. Oh my goddess, Willow can use magic again and for good... yay! Character development or hail mary pass?
Honestly, this is just Willow fixing things with magic again. We're back to the season 6 mindset, she's just using "good" magic now, but internally what has changed? The only difference is that Willow is in a good place now, that her friend's are cheering her on, but if she hadn't been is there anything that says that she wouldn't have gone dark again to "fix" things? Have we really seen her learn that much self-control throughout the season... we might have, had we gotten to see her more than the potentials, but as it is, it seems we're supposed to believe that a few months with Giles, hanging out in a garden, is enough to curve that wicked urge. So no, at the end of season 7 I can't say I see much growth in Willow. If anything, to me, she's the Willow of seasons 3 and 4, except that the only aspect she's more secure in is her sexuality.
And there you have it.
What you see as character development, I think is sloppy writing and character regression.
(I should add though that while in general I think the characters on Ats develop better Cordy is not included in that at all.)