Quote from buffntuff »It's mythic because it's dream eater for one less mana.
I feel like a lot of these "why is this mythic" complaints are just because the text boxes are relatively small and can't fit in a lot of abilities. If the card read "1U, exile this card: return target permanent an opponent controls to their hand. You may then cast this card from exile." or something then folks would be complaining less.
Dream Eater is a terrible comparison. This has a substantially worse body and gives you no card selection. No one thinks that if they had just wrote the Adventure text out they’d feel differently about its rightful rarity.
If you feel that a product is a let-down, why buy "one or two" anyway? That's not how you make your feelings known to a company. They can't read your minds, and likely won't see or care about your criticisms on some web forum. The only thing they understand is the bottom line, sales. If people buy a (theoretically) crap product, all they see is the money coming in regardless. If you feel a product is not worth the money, then don't buy it. That is the only sure-fire way to voice your criticism. 
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Then we would've been bored of them by now.
from MaRo's article two weeks ago:
"I've talked many times in this column about how planeswalkers are the most popular card type yet have the smallest design space. As such, I've spent a lot of energy slowing down how often we innovated on planeswalker design...."
continued:
"Back in Hour of Devastation, we had to design a Nicol Bolas planeswalker card. This was the end of Act I of the Nicol Bolas arc where Nicol Bolas shows up and easily defeats the Gatewatch. This was us reintroducing the character and establishing what a major villain he was. That meant we wanted a cool planeswalker card. A bunch got designed, but one of the most popular was one that had a static ability. Now, I'd been holding back from planeswalkers having static abilities because I knew once we let that cat out of the bag, it would be hard to put back in. Planeswalker innovations had to be doled out slowly, and this was a big one. (And yes, there are a few narrow examples of old planeswalker cards having static abilities—in this context, I'm talking about enchantment-like static abilities.) I made a compromise. Let's just make a four-loyalty ability Bolas in Hour of Devastation (we hadn't made one yet) and then when we made the next one in War of the Spark (we knew our major villain had to have a planeswalker card in the climatic set), we'd let that one be the starting point of static abilities on planeswalkers."
tl;dr: each set typically has 3+ planeswalkers. at 4+ sets per year, that's a lot of pw's printed; and there is only so much design space for the card type, so innovative designs have to be treated as a finite resource and released slowly over time or else they'll have exhausted all their tricks in a relatively small amount of time and struggle to come up with new pw designs.