I'm not saying that there aren't cool matches featuring U/W Heroic, but after playing 4/5 matches against it at FNM for like 2 straight weeks and seeing it in like 50% of an SCG stream like a month back I'm tired of it.
From personal experience playing against it, it's just so easy for them to curve out accordingly. Sure, if you
Thoughtseize them and have the removal to deal with their creatures one-for-one on time that's different, but if you don't, then you fall pretty far behind trying to deal with a steadily growing creature pretty much backed by 1 and 2 mana counterspells (
Gods Willing,
Feat of Resistance). And then if they're low on cards somehow, it's super easy to refill with blue Ordeal while growing the creature and applying more pressure. I just didn't like how easy it was for the deck to just rebuild on the fly or just run over decks with a single creature backed by protection.
In contrast, I love seeing Mono-Red right now in a world with Coursers, Caryatids, and all the manner of efficient red and black removal. There are just so many roadblocks and it's way cooler seeing them navigate their small guys while trying to push through lethal, where every life gained could be setting them back one spell or attack.