Implode

Five mana has been too expensive for serious land destruction since the days of Stone Rain, and bolting a cantrip onto a worse base rate does little to rescue a spell. Five mana to kill a single land and replace the card you spent doing it is a losing trade in any deck trying to win by mana denial: by the time you can afford it, the opponent has the lands it cost you to attack. What the design actually wants is a player who values the replacement card as much as the destruction, someone for whom blowing up a problem land (an opposing utility land, a manland, a fixer the opponent cannot easily rebuild) without falling behind on cards is worth the full asking price. That is a narrow brief, and it is why this never became the workhorse that cheaper, riderless land destruction did. The cantrip is the tell: when a removal spell has to pay you to play it, the effect itself is being priced as a liability rather than a threat. It belongs to a moment in the game's history when targeted land destruction was still being printed at premium costs, before the format consensus settled that mana denial either has to be cheap enough to set the opponent back tempo-wise or it does nothing at all.