Two 2/2 creatures for four mana is a good deal in Limited no matter how you look at it. But this card has an upside, which is hidden in its creature type.
Changelings are awesome! They synergize with any type of creature buffs, whether it's Bears for Ayula, Slivers for The First Sliver, or Goblins for Pashalik Mons.
Irregular Cohort will work in all these cases, which makes it one of the most valuable common creatures in Modern Horizons.