When it comes to difficulty, all factors come into play. However, I will admit that when I Personally say "difficulty" with the Zelda series, I give puzzle solving 67% of what I'm talking about. If the puzzles are essentially easy to figure out, I'm more likely to call the Zelda game easy. (Most of the time but not always. The older games I give enemies more credit). Why do I do this? Well, essentially everything in a Zelda game is a puzzle. Even fighting enemies is a puzzle because you have to figure out how to defeat your foe before you can actually do it. SS did indeed have foes that required a bit more timing, but the strategy to defeating them was easy to figure out. Most of the strategies for the non-bosses were also mainly the same. (Knowing when to swing your sword and bash your shield). Other games had enemies such as OoT redeads, WW sea creatures and a wide variety of foes that made you switch up your strategy moreso than SS. Now I'm not saying the exact same strategy is used to defeat every single enemy in SS. What I'm saying is that the difference of strategies for past Zelda games (mainly the 3D ones) had much more noticeable differences than SS. And even if the strategy in SS wasn't so obvious, you have a partner (like in a good number of Zelda games) who tells you how to defeat your foe. Honestly, I wouldn't have it any other way than to have a partner giving me knowledge, but for some reason, I felt Fi did this a bit more detailed than Navi or Tatl and because of that, she dimmed down the difficulty even more. I felt that while Navi and Tatl gave clues, Fi was a bit more direct though sometimes Fi would only give a clue and I'd instantly know what to do because I'd seen this type of strategy before.
Now if you put aside the enemies and just look at the puzzle solving itself, the concept of "SS is easy" becomes even more clear. Not TP easy mind you, but still pretty easy. Like Ventus said, the strategies SS implemented were in a lot of other games and Zelda games. If the emphasis of your game is puzzle solving and then you're not really solving puzzles, you feel like you're just going through the motions. Albeit, there were a few puzzles that get your noggin going, but the majority of the game was look at puzzle, instantly know solution, do it. I've actually excused TP for this as it is even easier than SS, but one thing TP had going for it was its creativity. You knew what to do in TP, but once it was done, you were still surprised at the results and not only that, but it was really fun!
"How do I get down this mountain? Oh, roll into the tree and ski that's easy enough! Oh em goodness! This skiing is awesome! I can swing my sword while I ski too!?! Shoot, I'm going back up and doing this again!"
Not that SS didn't have things that were different, but it had things that weren't as unexpected. A toy beetle is interesting, but... not too out there. I've seen out of place machinery in Zelda before and I've been able to control objects from a distance before. However, a cog that lets me ride around machinery like an amusement park ride... I never would've even thought that would be in my game.
I'm diverting a bit here, but to get back on track, SS was easy to solve. The main thing it had going for it difficulty wise was that its enemies were a bit more intelligent, but their strategies aren't too complex nor too different from each other. Once you figured out the strategy and get the motion controls down, all it took was patience. I compare SS to TP because while I too felt TP was even easier than SS, it cushioned its easiness with creativity. Without that, I simply can't look past the SS's easiness.
(And all this is excluding the argument about things like dowsing and gossip stones).
