Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step, even if the player it was attacking has left the game or the planeswalker it was attacking has left combat
That said, there are times (especially just after rotation) when cards that are not that great are played just because of a lack of better options, and cards with a high potential that take time to find their potential
Simply choose an Elite Trainer Box from a recent set that you like
9 Rousing Refrain Play The Long Game If you dont need the mana immediately, you can try playing Rosing Refrain in your deck
As Hall of Famer Reid Duke perfectly put it, the card made blocking the fundamental defensive action in MTGs rules a fools errand
One major advantage of this Leader is being able to use the effect of "OP05-067 Zoro-Juurou" immediately, since you start with three Life cards