Omnath is definitely powerful, but it doesn't really point anyone to a given deck. Sure, it's got the Landfall text but it isn't really a Landfall card as much as it is a Goodstuff card. Like even if I can't maximize Landfall triggers in my 4-5c Goodstuff pile, I'm rewarded for casting it (drawing a card) and then next turn I just get a free 4 life off my normal land drop. If someone's playing aggro against this 4C Goodstuff deck, they're just fucked by this roadblock + lifegain doing a super
Courser of Kruphix impression. I don't even have to build around it; it's just fucking good and rewards me for doing the bare minimum to develop my board.
With
Lotus Cobra at least it opens up the possible line of maximizing a fetch if I sequence spells right for a
Black Lotus turn to power out something ahead of curve, but Omnath just does too much for too little.
I'm playing it all day in EDH decks that can cast it, but that free generic value is way less interesting in Cube for me.