While I don't disagree with such quotes by any means, the problem is that Walt made them with the assumption that the new elements would be improvements over the previous attraction. When he was in charge of the company (and for some time after his death), this was a fair assumption. But in the past couple of decades, it has sadly become naive to assume they'll create a worthy replacement for any classics they replace.
Epcot is a perfect example of that still ongoing problem. Absolutely none of the attractions that replaced World of Motion, Horizons or Imagination have come anywhere close to being as good as those rides were (essentially every single change made to the park post 1994 refurb of SSE has been a major letdown if not abject failure). And with more and more creative talent being purged from the company, continual short sighted and crippling budget restrictions, and physical show sets and animatronics being considered "passé" by the company (now being replaced by video screens), it has become even more dire for new attractions replacing older ones. At the very least in regards to WDW.
If Disney actually came up with a concept wholly superior to Jungle Cruise and gave it the budget and talent it needed to succeed, then i'd agree with that completely. But I am not at all convinced that the current leadership is capable or willing to do that at all. If it can't be assumed that what we'll get as a replacement will be better than what was there, then the original needs to be preserved until someone else is placed in power who is capable and willing to do such a thing. Otherwise we're just likely to get dumbed down replacements ala Epcot.