Each time you draw a card, you put a loyalty counter on it, and the tokens Teferi creates also get +1/+1 counters
These sorts of Jund decks have been a staple in Standard for years, and its difficult for a deck full of small creatures that need to work together to win to beat a monstrous pile of removal and unbeatable creatures
Red decks are good at creating explosive turns, securing an early advantage, and just generally controlling the pace of the game through disruption, constant pressure, and a bit of calculated chaos
However, the more cards you have in your deck, the lower the chances of you drawing your best cards
Before, in formats like Modern, while the removal was good, you could play around it or attack from an angle that was less susceptible to it
The only reason Zulaport Cutthroat beat out Blood Artist is that it is a 1/1 rather than a 0/1, and has three creature types that can all work well in black Commander decks, over Blood Artist's lone Vampire typing