The London Mulligan will be the official mulligan in Magic starting with Core Set 2020. Great. We tried it in Commander and it was completely fine. And it was also good in Pauper. Of course, there are certainly a few decks that benefit excessively, but that can be regulated otherwise. The new mulligan simply helps to avoid "non-games" due to multiple bad starting hands. There's nothing more annoying than losing a game in the mulligan because every hand was without lands or only lands.