The biggest problem would be exile, a creature spot removal, or a deck that ran a heavy amount of counterspells
Second, it will always give your opponent a free nonland card
So many players found themselves switching to Magic the Gathering Online because of those reasons, it wasnt cheap either as you had to buy the cards anyways, but it was a least a cheaper option than playing paper magic
Fortunately, there are several cards available to keep the counters around , even if the creatures die
A very powerful commander, perhaps even the best mono-black commander out there, Mikaeus can pump your zombies and make it basically impossible to remove any of them
Nissa is better in the midrange and control matchups than Courser however