In general control decks struggle to deal with threat quantity and speed
With the set focused on Indiana Jones-style ventures into long-forgotten ruins, it only makes sense for Magic to produce a new mechanic centered around new discoveries
If you wish to introduce a new stage card, you must replace the existing one
Plus, players might likely be more than interested in replaying its ETB effect over and over than anything else
Staff of Eden, Vault's Key is another one that seems out of place in any AC Commander deck but is incredible with Etrata since we're cloaking a ton of cards off our opponents, so this is a reanimate + absurd repeatable card draw
Of these, Pestilent Cauldron is the worst since it requires discarding a card, which keeps you on card parity