Very true. Although I don't like it, every location that we visited in the last 8 years no longer exists as we saw it. Mata Nui was destroyed by Rahkshi, Bohrok and then a face, Metru Nui was destroyed by The Cataclysm, Visorak and then the OoMN, Voya Nui destroyed itself and Mahri Nui, and Karda Nui filled itself with a giant non-stop energy storm. The story team seems to like to leave no traces.
Of course, seeing as SM blew up into 3 parts, yet inhabitants and structures survived, which could be due to the power of EP that everything wasn't obliterated, it may be possible to reverse the process through EP again. EP is kina like the BIONICLE "a wizard did it" excuse.