My opinion on SS has definitely changed a fair bit over time. Back when I first played it (upon release), I was fully hyped for it as I didn't have a good point of reference for what Zelda games are typically like. Even if I never finished it, I still thought well of it as a game, because I didn't notice the glaring issues it has.
Coming back to the Wii version when I was much older, those issues made themselves very apparent, and prevented me from having any kind of motivation to want to tackle it again.
Now, with SSHD, the biggest issues keeping me from continuing with the game are mostly addressed. Those being the frustrating motion controls, Fi's overwhelming presence, and the amount of downtime/interruption of the game's pace in the early game.
Surprisingly, my thoughts on SSHD through the early game were more positive than I had expected. I was appreciating how Fi wasn't there at every turn to explain to me something I already knew or had the intelligence to understand on my own, the events of the game were moving along at a better pace thanks to faster dialogue and skippable cutscenes, and I was able to not get frustrated about the controls because button controls were an option (though I have played a decent amount of the time with motion; they're still just as irritating if not worse because the gyro drifts so much).
But getting into more of the mid and late game has reinforced that, while SS has some good aspects to its design, there are still negative ones that couldn't be fixed without significantly changing the game's design. First and foremost, the lack of a proper overworld and the decision to make the world that's there a system of hallways and restricted areas leaves the player feeling cramped when their only other option is to fly through a mostly barren sky, complete dungeons, or maybe just walk around small locations like Skyloft or the Lumpy Pumpkin. It feels like you never get a real break from dungeon crawling when the "overworld" is designed like a dungeon itself. Past games had things like the Great Sea or Hyrule Field to bop around in as a break from dungeon crawling, but SS doesn't have anything like that. And considering you have to return to the same places over and over again, it only makes things worse. I personally don't care for that approach at all. It kills the sense of adventure for me.
Speaking of dungeons, I can't say most of them have impressed me, with either the dungeon itself or the bosses. Ancient Cistern is probably the best of the bunch so far. It's solid, though I'm not too keen on Koloktos as a boss. Bosses in particular are fairly disappointing as well. None of them are particularly fun to fight for me, though I like the concept of Ghirahim being a duel between swordsmen (though Scervo is a better execution of the concept if you ask me, despite being a miniboss). The Imprisoned is awful. There's a reason that fight is generally considered bad, and I'd wholeheartedly agree. Other than the Silent Realms, the Imprisoned fights (2 and 3 specifically) are one of the few times I've raged at the game.
As far as the game's pace is concerned, it's never very good, IMO. But the mid-to-late quests like the Scrapper escort in Eldin or the Tadtones segment just feel like padding to extend the game's play time. They're not mechanically bad I wouldn't say, but it causes the game to drag for me. I'm at the point now where I'm just actively wanting the game to end, even if I have enjoyed my time with SS overall.
Combat (one of the things I was most interested to see how SSHD would handle) is not bad, but it's still no replacement for a simple Y or B button press to swing your sword. I get that Nintendo was pretty stuck with how they could fix it given how SS is built around the motion controls, but I don't enjoy fighting with either control scheme. Ever since I got the bow, I generally just pick off enemies (when possible) to avoid having to deal with sword swinging. I'm glad it gives more people the chance to play the game, but I still can't get into it. It works, but it doesn't work well enough for me personally.
I've pretty much been exclusively negative in my thoughts on SS so far, but I do have praise for the game. I think the presentation is lovely, and the music suits each scene well. Attempting to tell more of a story is nice, though it's fairly uninteresting to me. The visual style itself (character designs aside) is very pleasant. I've always thought that, and SSHD has only enhanced those visuals. Certain locations are also quite unique in their designs, such as the Lanayru Sand Sea and Eldin in general. While I don't care for the restrictive nature of the regions in the game, I don't deny that some of them have some rather good choices for their layout. I think item use is also one of SS's strong suits (sometimes). The bow and clawshots in particular are always very fun and satisfying to use. Likewise, the introduction of new mechanics like stamina was ambitious, even if the execution was lackluster, IMO.
This has become much longer than I meant it to, but I kinda needed to explain my thoughts, I suppose.
On the whole, I think SSHD is the best/definitive version of the game, and that SS is a solid enough game itself. But playing SSHD has me considering it to be the weakest 3D Zelda I've played. It's worth experiencing in full once, but I feel no desire to return to it again.