The thing that makes it complex is that nearly every time a card is placed or used (two different actions, for the record), there's the option for the other player to counter with another card, and many have multiple obscure abilities. That's not to mention the character cards' abilities to augment and block one another, or team affiliation, evasion, reserves, concealment... the list goes on. Luckily, there are massive tutorials, but you'll need to watch each several times to fully absorb it all. In the meantime, you'll probably take quite a few lumps.
This being a card game, difficulty is very erratic even if you do know what's going on - you might win two matches in a row, lose four times, then win three more - it's often all about the luck of the draw, especially early on. And for the record, we absolutely found ourselves drawn to Marvel Trading Card. It's just that the intense complexity and cramped screen real-estate kept it from being the accessible, instantly lovable smash-bang, super hero-em-up that the comics themselves are.