Despite the seemingly broad range of effects on this Charm none of them are very powerful and all of them are highly situational which results in a poor performing card
In something like a Vespiquen deck that interacts with the discard pile Unown is even stronger, because it discards itself for free
Lier, Disciple of the Drowned gives you extra turn spells get flashback, so every extra turn is actually two
Creatures also often have 'Lords', which can buff an entire MTG creature type
For Auras, I count 22 aura cards, not including Eidolon of Countless Battles which can be cast as an aura and Scriv, the Obligator which creates aura tokens
Now that the spoiler for Kaldheim has been out for a few days I've had a chance to create my Top Ten list for the best cards from the set for casual, multiplayer, and Commander