He notes blind spots (selective land kill, stack interaction) and offers picks and a Moxfield package
For example, if we look at a card like Mindbreak Trap, it says exile any number of target spells. It would be to powerful if you could exile any number of creatures on the battlefield, so this only refers to cards that are on the stack
Conflux Nowadays, we have plenty of five-color legends, but back when Conflux released, they were fairly scarce
Wheeling away your hand when it enters shows you lots of cards and stocks the graveyard (and perhaps triggering some discard synergies), then the second ability sets up your board to become incredibly threatening
As proven by Austere Command, the ability to be flexible in what needs to be killed greatly increases its power even if it is killing creatures the large majority of the time
Hell, you could literally have every card on this list in a deck with Esika as the commander