Nothing rude meant by this (honestly), but if the experience of discovering the island, finding and completing the puzzles itself isn't motivating enough then perhaps it's just not the game for you?

I understand your point about filler, but the puzzles are the game, and if you're enjoying them then it probably doesn't come across as filler, just more to get stuck in with (though I do wonder whether so many slight variations on a theme are required in certain areas).

Hyped it may be, but that doesn't mean that you absolutely have to enjoy it at all costs. There are other games, and other developers :)