It's not just huge, it doesn't just not have an upkeep and not have a restriction on untapping
We very much shy away from using rarity as a means to show something is out of color, because a tournament-viable rare will be acquired and thus become the poster child of the color
Against them, this will destroy 3 things and probably grab you a random creature, which is well worth 5 mana
Dislike relying on your commander as a primary value engine
This often creates two or more colored mana on turn one, and continues to scale throughout the game with no downside or additional costs at untap
Now, not all game pieces are created equally, and some of the more divisive ones have become the poster children for Stax and thats before I even get into how people are more than willing to throw taxing effects under the same bus