It somewhat boils down to there being loads of things which draw you cards when dorks die and so you just play those over this and better sac outlets that don't cost two mana a time
While he is actually kind of a bad duelist (Mai and Joey both should have beaten him, that was bad writing), every other aspect of him makes him a great villain.
While one of the goals of Modern Horizons 3 is to shake up Modern with the introduction of brand new cards, this set also has the New-to-Modern bonus sheet, which contains reprints that will become legal in Modern for the first time
Playing a new one causes the previous one to be put in the graveyard
If this card is in your GY and your opponent controls no cards in their Spell & Trap Zone: You can Special Summon this card in Defense Position, but banish it when it leaves the field, also you cannot Special Summon monsters for the rest of this turn, except Winged Beast monsters
According to Rosewater, neither MTG color has had much to do with Convoke in the past, so "there was some new design space to explore"