I played Magic briefly as a teen and the thing that bothered me the most was how mana worked and the tendency to either get mana flooded or mana screwed. I even played a custom format with friends where you separated your deck and your mana into two decks and drew one from each every turn. It made the game much more enjoyable and consistent.
That being said I personally find the variance that Magic has when it comes to mana resources to be more interesting than the alternatives as most of the newer card games have abandoned the idea of having mana resources(lands) in your deck all together. I think the lands are one of the main things that makes Magic an interesting card game.
One interesting alternative to lands was from the World of Warcraft Card game (spiritual successor to Hearthstone) which allowed you to play any card from your hand face down as a mana resource. Although they completely did away with this in Hearthstone so they could limit the deck size and the reduce the number of duplicate cards that were needed in each deck.