Pointless?
Advantage with an ability check round after round after round is very potent. It's like an unlimited number of more powerful than a cantrip spells. And it's not like most PCs wouldn't get the feat at level 4 or higher where it doesn't take long for a melee PC to get two attacks per round.
Being prone also has disadvantage on attacks, so it defensively helps the PCs. Attack the foe, shove the foe, and if prone, move to some other part of the battlefield and the foe has a disadvantaged opportunity attack. And even at level 4, other melee PCs would still get advantage on melee attacks.
It is very very far from pointless. It is one of the nicest feats in the game for sword and board, even without getting every single melee attack when it works with advantage.
Standing doesn't cost anything if you don't have to move far. Being prone only grants advantage on attack if the attacker is within 5 feet, anyone further has disadvantage.
Why would my tank want to move away from the target? If I do, the bad guy stands up and either does a ranged attack, does a tactical retreat or just moves around me to get to the squishies now that I've removed all disincentives.
If I work at it hard enough I guess I could come up with a scenario and set of builds where it would make sense but you have to build the party around that particular niche. You have to make a lot of assumptions before it buys much. For the vast majority of combats and builds, it's virtually pointless.