I'm a fan of Once Upon A Time, but I agree with that assessment.
I love the first three seasons. Their version of Peter Pan is one of the best vilains in anything. Such a clever new take on an old character.
Pan was great and I loved his genuine friendship with his second in command Felix. However, I kind of wish he wasn't made to be Rumple's father because it just started to become repetitive with the villains being related to the heroes. Literally it's this:
S1- Regina
S2- Regina's mother plus grown up kid who Regina screwed over and Neal's fiancée working under Rumple's father
3A- Rumple's father
3B- Regina's sister
4A- Emma's foster mother plus Rumple
4B- Rumple plus the queen's of darkness
5A- Emma
5B - Zelena's true love plus Rumple
6A- Rumple and Belle's son
6B- Rumple's mother
S7- Ultimately the mother of AU Hook's child.
However it definitely lost it's way in series 4. There were some good things that year like Cruella De Vill who was hilarious, but really apart from series 6 which I liked a lot, seasons 4-7 range from average to dreadful.
Season 4 was "insert Frozen here". They literally cut and pasted the Frozen characters from the movie. I found Anna extremely annoying, especially how they put her in Belle and Charming's flashback and had her be their inspiration. The Frozen arc had the opposite problem to the Neverland arc. Whereas the Neverland characters were under explored due to lack of flashbacks (So much wasted potential), the Frozen arc inserted Anna in flashbacks where she didn't belong.
Also Neverland should've been Hook's time to shine yet he was pushed into the background but they put him front and centre in non-Neverland related seasons. We should've had flashbacks to Baelfire's time in Neverland, a bit of background on Felix, how Tinkerbell got to Neverland, etc. So much potential yet the half-season made it impossible to give the Neverland arc the justice it deserved. Also why couldn't they have had some daylight scenes in present day Neverland instead of having everyone stumbling around in the dark. Also Storybrooke shouldn't have been neglected.
The author plotline was stupid. Henry was the least interesting character and they could've easily explained away the book as created by magic during the curse to show the "real" events.
They never let RumBelle be happy on-screen. They were only ever falling out then reuniting. Rumple was used as a placeholder villain even when there wasn't really any reason to be.
The CaptainSwanfire triangle was shoddily written. The killed off Neal which meant that Hook won by default rather than Emma actively choosing him. Hook's behaviour was awful up to Season 6 and early Season Emma would never go for someone like that. I've never been a fan of Hook (especially because of his treatment of Belle), however he deserved so much better than Emma in Season 6. Emma was character assassinated into being really self-centred and kind of bunny boilerish. When Belle goes to Granny's wanting a room, Emma just says to her "you don't want to stay here" then just walks away. Not only is that insulting to Granny but she doesn't even offer Belle somewhere to stay or recommend an alternative place. It is up to Hook, the guy who has treated Belle poorly in the past, to step up and offer Belle a place to stay on the Jolly Rodger. Another time is where Hook discovers he killed Emma's grandfather in the past and he wants to confess so there's no secrets between them. He gets home and doesn't get chance to say anything because Emma practically forces him to propose then and there because she'd gone rooting through his stuff (for no reason at all) and found the engagement ring. "Run, Hook, Run!" would've been sound advice.
OutlawQueen was a complete train wreck. Not only is there no reason why Robin Hood would be so into Regina upon first meeting her (since he would've only known her as the evil queen plus it was so awkwardly funny seeing him help Regina off the ground whilst leaving a heavily pregnant woman (Snow's actress was pregnant even though Snow wasn't meant to be at that point) on the floor. Then they had it turn out that Regina was responsible for killing Maid Marian so Robin was in a relationship with his wife's murderer. When Marian was slowly freezing to death, they continued having Robin umming and arring over whetehr he wanted Marian or Regina. Then it turned out it wasn't the real Marian etc. THEN it turned out that the "destined" relationship wasn't actually that version of themselves but an alternate version and the alternate version of Robin was way more interesting than the main timeline Robin.
They seemed to change their mind on the reality of the AU. First it wasn't real which is why Regina was "allowed" to kill AU Snow and Charming, but then it was made real which means Regina just killed two people and yet none of the heroes bat an eye.
Snow was character assassinated. She went from being an idealistic warrior to a nagging harpy. Her insistence that Charming drop everything to meet the mid-wife was demanding and she was kind of thick. The only way it would've been more obvious that Zelena was the wicked witch was if she carried a neon sign.
I dislike what they did with Regina. Redemption doesn't mean the sun shines out her backside. Crowning her the "good queen" at the end was such a cop out.
Cruella De Vil was great. I particularly liked her in the DVD extra "A knight with Cruella". One scene and I was already shipping her with Mordred (JM's character). They had way more chemistry than Robin Hood and Regina did.
Robert Carlyle and Emilie De Ravin knocked it out of the park in Skin Deep and Beauty where they made RumBelle Ellie and Carl from Up.
S7 was an awful season in every way. They had no idea where to go with any of the characters, and the villains were so boring and lame that they literally just brought Rumple back as a villain in the last episode for no reason.
I've not actually seen Season 7, I've just seen clips of it on youtube. I'll have to get the DVD at some point to watch it and thus complete the series.
Henry is such a boring character. I know they got the guy out of the Walking Dead who played the camel (he was good) to play adult Henry but the character is so boring, I don't know if he could do much with the role. They had an alternative universe Cinderella which is ridiculous because it undermines the premise of the whole show. The characters in Storybrooke are supposed to be the "real" versions of the fairy tale characters rather than the stories about them.
This is the main reason I hope they don't start bring AU versions of existing characters into the MCU, it kind of undermines the existing characters the audience have grown to love.
They should have used The Horned King I think as the main villain at some point.
Horned King's Death
He'd have been a great villain and there is no way they could have tried to make him just another "wanting to be loved" villain again.
I think there is rights issues to using the Black Cauldron characters or whatever book that was based on. Mind you, given what they did to Chernabog, it was probably better they didn't attempt the horned king. They couldn't even keep Chernabog's size consistent. He looks huge on the clock tower roof, yet when he's attacking Emma's car, he's small enough to perch on the car roof.