Reusing terrain design is not inherently bad if what is done in that terrain is different and ingenuity/creative to an extent. Even if you do things differently, if what is done is expected or feels boring or tedious, then you've got a bad design and really that goes with any design concept. The forest and the volcano are cases of where a good many people felt that the area had really nothing breath taking to give out.
Barring the water portion - which I liked to some degree - I think
Skyward Sword did an excellent job at breathing life into previously visited areas. Older games in the series had areas that weren't even worth revisiting at all; they seemed to die after just visiting them one time and completing whatever there was to do in them... :/
The first travel through the woods involved hiking from point A to point B which is mundane.
Yeah, typical starting location in a Zelda game.. :/
The difference that it brought was that it later aloud you to swim in its entirely flooded area, however the idea of being able to swim in Zelda has been used and it could be seen as another water level or dimmed down version of MM's great bay considering how well the swimming was done in that game. Added that to the concept that the only reason for swimming was a fetch quest with no time limit or sense of alarm and you can leave a good number of people unimpressed.
I agree that the swimming portion felt forced; it was simply a great concept that was executed poorly. It almost felt as though Nintendo needed an excuse to make use and/or show off what swimming would be like with motion controls in a Zelda game (don't bother bringing up TP; it was merely a port, and its motion controls were tacked on). What you lost me on, however, is the idea of swimming being a reused ability... Dunno about everyone else, but I could have sworn that swimming is a basic element of an adventure game. That being said, it is not exactly an idea that should be thrown by the wayside if Nintendo can help it. Although, I could be missing something. Perhaps you should have worded it differently.
The Volcano again involved hiking from point A to point B which is not very fun. New things that it brought include digging, which has been done before in MC. It also brought about sneaking without having your items, which has been done in WW.
I fail to see where you're going in regards to the lack of ingenuity in the Eldin region. You mentioned several ideas/concepts that were not boring and/or overdone, but were actually quite fun, innovative, and creative. For instance, the weapon-less stealth portion... you mention it being done before in
The Wind Waker. However, you fail to address the innovative and unique qualities that this "reused" idea brought to the table in SS; there was far more. Not only did Link lose all of his weapons/items, but he also had to endure a multi-tiered climb on a volcanic mountain, while making use of advanced skills that were not present in WW. If anything, SS should be given kudos for expanding on and putting a new spin on the idea to such a degree; essentially giving us a glimpse into what the WW's stealth portion
could have been like...
I also would like to address this:
So while these ideas from the past were put together, really we've seen all this stuff before.
You make it sound as though Link is taking a leisurely hike through Hyrule Field in TP. Its as though you blatantly left out the multi-tiered qualities of Eldin Volcano - the lava pits, the slippery slopes, the many impediments, etc. And of course the concept of digging underground has been used once before. What's Nintendo going to do, abandon a great idea, and fail to expand on it? That, to me, would have been a bad idea, especially in the Zelda series, as Nintendo is notorious for building on old concepts in creative and innovative ways. Also, I am sure that digging underground is something that many fans have wanted to see in 3D.
The best argument that can be given is the desert because while Link has traveled through time and operated machinery in the past, for some reason no one ever expects to see these futuristic concepts in a midevil themed game.
Mentioning the time-travel aspect of Zelda as a reused concept is rather weak. The time element and the many forms it may take should be expected in the series. Also, the timeshift stones have been regarded by many as one of the greatest ideas in the series. Some even argue that the concept is among the greatest in all of adventure games. While I wouldn't go so far as to agree on this, I do regard timeshift stones to be the most innovative time-based devices in the series.
Last but not least, the Zelda series is NOT wholly based around medieval times. Don't get me wrong, it features many elements from it, but much of it has been shadowed by newer concepts since the days of the original LoZ. SS is the best example of this, as it features many elements from Eastern concepts. In other words, much of its story content was heavily inspired by Japanese mythos...
Going further... A little known fact is that the concept of futuristic technology being found in an ancient setting was borrowed from the real-world research of mythical cities like Atlantis and Machu Pichu, which have been noted for their advanced technology and architecture. This theme is used in many forms of media to instill a sense of majesty and adventure into the reader/watcher/gamer, as well as appeal to their imaginations. It can also be regarded as one of the greatest forms of irony in the Zelda series, given SS placement in the timeline.
Redone themes are fine as long as they bring something along that is both unexpected and fun. In fact, I encourage redone themes because they help stick to the traditions of the game. But when redone themes are used and incorporate things that may not have been used in that terrain before but aren't really new or just not that fun, then you have a problem.
I'm sorry, what?