While its plenty powerful, its the effect on perceived barrier-to-entry that really posed a problem because casual players watching Commander games in passing could reasonably assume that they needed hundreds (now thousands) of dollars in Power-9 mana as table stakes, just to join the format
In standard mode the player's deck can only use cards which are legal in the current standard rotation (each year older cards are retired from play)
+1/+1 counters synergy : 21 cards Benthic Biomancer, Deeproot Elite, Forerunner of the Heralds, Herald of Secret Streams, Tributary Instructor, Zegana, Utopian Speaker, Prime Speaker Zegana, Ripples of Potential, Inspiring Call, Quandrix Command, Fuel for the Cause, Wave Goodbye, Hardened Scales, Simic Ascendancy, Bred for the Hunt, Forge of Heroes, Littjara Mirrorlake, Llanowar Reborn, Novijen, Heart of Progress, Oran-Rief, the Vastwood, Nicanzil, Current Conductor As we can see we have a strong presence of +1/+1 counters strategy cards
Young Pyromancer and Guttersnipe trigger every time you cast an instant or sorcery, netting you additional creatures and damage.
It is a source of lifegain and good disruption against any graveyard goings on
For example, discover 3 would allow you to play either Promise of Aclazotz or Foul Rebirth, but not both