Risk and reward are both important elements of playing
League of Legends. If Riot released a new champion who could just instantly teleport back to base without any risk whatsoever, players would be screaming that it was overpowered. As it turns out, several champions
did get that ability due to a Recall bug so severe that
Riot Games has temporarily turned off Ranked play whilst the bug gets sorted out.
While it’s not an offensive bug, the fact that you can cast Recall instantly with multiple heroes means that said heroes can instantly teleport out of danger and thus greatly disrupt the metagame. An update on the issue should be available shortly.