There are other people who vent out loud instead of typing who would cause some initial problems, but I'd also argue there's also a difference between a Discord server where you are with friends or a community you know vs being with complete strangers you'll never talk to again.
My bigger concern is that it'll be impractical to mute players. In my experience on voice chat, it's not uncommon for someone to only say a MIA instead of ping it. In looking at the LCS it's not uncommon to do the generic blue dot ping (since that's faster) and say what you mean. Combine both of that with having to mute someone and you're completely I'm the dark if you mute a player.
And before you say "people will continue to ping", remember how much of a stir has been going on over auto fill, a "feature" we basically had for 5 years and was only missing 1 year. People get use to the lazier system (only 2 roles, speaking and blue ping) and won't continue to practice the other way (other 3 roles, using all the pings). Take a few videos of pinging today and compare it to 1 year after voice chat comes out, I promise there will be fewer.