It should be retitled as 'MTG is the most complex game we've played'. I would counter that other card driven games like Android Netrunner, Terraforming Mars, Lisboa, Hanabi, etc are just as or even more complex.
MTG has ways to return to a previously seen play state, technically allowing a game to continue infinitely, depending on your deck, of course.
By game theory they shouldn't; eventually a player will be able to end the game while ahead and should do so; but we're already disregarding the motivation of winning for MTG.
(An expansion introduces a rule that each round automatically advances one of the game-ending parameters, but says you can play either with or without that rule.)
In TM there is almost no re-using of cards. Once a card is played, it either is discarded (red), provides a one-time bonus (green) or provides passive/active effect (blue). Only blue cards could be considered as being re-usable, but even that is only as far as the actual passive/active effect goes (which is separate from the effect it may generate when entering the game). Compare it with MtG, where many cards provide effects which allow discarded cards to be returned to the game (ranging from simple "ressurect creature" effects to such that allow shuffling whole stack of discarded cards back into the deck).
Also there is no stack in TM. And gaming the stack to your advantage is one of the core mechanics of MtG. A card you played may have different effects depending on cards your enemy plays in response, and these may have their effects altered by the cards you play in response, etc.
When it comes to cards themselves, and their effect on gameplay, it blows netrunner away.
Just look how effect layers are constructed, or even a simple stack and priority itself, not to mention infinite loops.
I do agree that i had way more fun playing Netrunner, mostly because you cannot be mana screwed/flooded like in mtg - as you can spend action to get resources or cards.