Mental Misstep is better in legacy and the like but in cube there isn't enough
Having all cards from all the sets will make easy to file multiple decks like those needed for the recent Triple deck Constructed format used at Worlds for example or to come up with very effective strategy in the Infinity format that will still use all cards ever released in Lorcana after Set Rotation kicks-in
It's like any mass removal spell, if you want to sweep the board, then you'll likely sweep your own stuff too, especially with White
When these elements come together, the result feels cohesive and trustworthy
Commander 2019s Merciless Rage uses the madness mechanic a lot, and it turns out that cards cast with madness are technically cast from exile
If the number of differently named lands you control changes while activating mana abilities (probably because you sacrificed one or more lands), the cost to activate the ability remains what you previously determined