Maybe its because I only played the first 2-3 hours worth of Galaxy, and maybe there's more variety and crazy-awesomeness later on that I don't know about, but if what I saw in those first 2-3 hours are simply minorly altered as the levels progressive, while retaining the same game mechanics, then I can understand what Miyamoto means by his comment on "conservative design."
If you think about it, gravity-based games have existed even since the NES era, so there's nothing really new there. Rounded platforming levels is neat, but already done before as well. Then you have the puzzle platform levels, which Sunshine did.
I was really expecting the gameplay to blow me away, but instead, it was just making extensive use of the wii controls, and that was more or less it.
His comment on TP also makes sense, since while it was a brilliant game, it was definitely missing something. Even at the 50 hour mark, I felt like I was missing something. I think they needed one more dungeon or something (or at least, that's how it felt, IMO).
And the ending didn't help, either.
Reading the article, I'm disappointed that he didn't ask more on Miyamoto's opinions on hardcore games, or expand on at least Portal. Seems like a lost opportunity, since it looks like he showed interest.