Im going to let you in on a secret: Top card magicians use marked decks
Every pack also comes with at least one Traditional Foil card of any rarity, while 20% of packs swap in a Traditional Foil Land
Though this Ajani's +1 is rather lackluster, only gaining you three life, its -2 more than makes up for it, bolstering your entire board by putting +1/+1 counters on each of your creatures and loyalty counters on each of your Planeswalkers
Sure, each half costs one mana more than the split half, but you can add in interaction in your creature spots or a creature in your interaction slot and then a beater later to close out the game, and you can get both effects for one card
It was close last time out, being tied for third place, and obviously it's one of the most powerful cards ever printed, but what changed to push it to the top
Other artifacts you control also have hexproof and indestructible, which is a very fun ability when it comes time to combat