To be honest it sounds like most of the players who don't want this addition are the dedicated pc players who want to grind fast wins for leaderboards and levels. As a Java pc player my self I can only imagine how easy it is to fight against mobile players for example when you become really good at the game. Games will become way harder for pc players and maybe even for console players who often got against mobile players after this update, so obviously grinding for leaderboards also becomes slower for many players.
So with that in my mind, I don't think it's a bad addition to the game. I don't see any other harm with this update except that the better pc players don't get free and fast wins against mobile users :p
Also I'm guessing that this is a Bedrock only thing so far, since skill based match making could make game queues too slow for the Javas lower player count?