The game has some really high highs and some really low lows. There are a number of aspects that are the high point of the series, but it's saddled with some really poor design choices. To improve SS would be the truest form of "addition by subtraction". Motion controls are overused; the sword-fighting was really good, but all other implementations were unnecessary and/or overly intrusive. It has an insulting level of handholding and tutorials that you can't avoid. And it's the worst offender in the series when it comes to the "between dungeons" content. Skyward Sword has the most filler content, which felt necessary only to pad the game's length.
Scale back motion controls (or remove them altogether), remove a lot of the annoying handholding and trim the fat, and this would be one of the best Zelda games. So I get why people really liked it, the great qualities are there. But a number of reviews really overlooked a lot of the pacing issues. There was one review I remember reading (that gave it a 10/10) that praised the pacing, and let's just say I don't agree with that whatsoever. It would benefit so much from being a lean, 20-25 hour adventure, but you know how it is...games gots to deliver those long hour counts.
I'd give it something like an 8.5/10. The good far outweighs the bad, but the bad aspects are why Skyward Sword is merely a good video game, and not the all-time classic that it could have been. I played this game through twice at launch (once in Hero Mode) and nearly 10 years later I've never had the desire to revisit it. I'd love to replay just the dungeons as I have a lot of fond memories of them, but having to play the entire game again? Forget about it.