Tempo decks, and aggro decks in general, often cant keep up on card parity as the game goes on and your spells get subjectively weaker
The 40 HP extra isnt bad either, especially with their flagship move Outrage
If attacking is off the menu, the treasure tokens created at the end step can still fuel a gigantic Souls Fire or push Reckless Fireweaver into working overtime
In all but the most aggressive matchups, this can tag all sorts of relevant plays while providing virtual card advantage
Muldrotha works particularly well with cards that sacrifice themselves for effects and Sagas, which have a built-in time limit until theyre put into the graveyard
Selesnya decks are not short on tools for their players, and usually establish a game plan through powerful nonland permanents