On the other hand, mythic characters can grant spells (starting at 3rd tier!), and become immortal unless killed by artifacts (at 10th tier) so they sort of ARE demigod-level in some ways.
And the KIND of stuff it lets you do is actually extremely impressive in a lot of places... especially some of the augmented mythic spell effects (baleful polymorph with a 1-mile-radius area...) - they're really expensive in terms of mythic power, but super impressive.
I agree the mythic monsters are kinda underwhelming.
It's very much geared toward mixing mythic levels in with regular levels, not just adding them on at the end... the sample adventure is 7th-level/3rd-tier. (And it's very cool, with mythic dinosaurs...)
It's really cool, but it's not the Pathfinder ELH.