Looking beyond cards that directly reference +1/+1 counters, these decks can and should make ample use of cards that care about modified creatures
You may play lands, and cast spells from that players hand this turn. This is on a five mana Esper 3/3, so the cost and body arent great, but if you want to make sure you lose a game of Commander before you even get to do anything, have this as your main card
With the 1996 World Championships, we got a corresponding 1996 World Champion card
And again, you dont even have to plan for the most likely way to see more than half your deck in Standard, which is What if Soaring Thought-Thief mills my search targets? But five cards is a lot of sideboard space to use these days
Since you get a bonus once with the Magecraft effect, it's easy to win on two fronts along with the stat boost