It taps for a sizeable chunk of mana, but the catch is that it can't be used to cast spells from your hand
You can use as many as you want - even all five
And of course, the biggest application is to attack with everyone, untap your creatures, and spread the +1/+1 counters around
Magic has innumerable interactions that each recontextualize the game-state, sometimes to the degree of utterly unforeseen terrain
Secluded Courtyard on the other hand, is an upgraded Unclaimed Territory since the colored mana can also be used to activate Creature abilities
Chief Marketing Officer for TCGs at Ravensburger Elaine Chase said, No card is ever designed with the intention of it not being played in competition, but in order to keep the meta-game healthy and challenging without it feeling stale or repetitive seeing the same strategies again and again, the TCG design team at Ravensburger made the difficult decision for the good of the game