One of the most vivid memories I have from vanilla is me and a couple of my guildmates hearing about the GearScore addon for the first time and laughing at the absurdity of it. Mind you we were a raiding guild so it's not like we didn't care about the quality of players, but it was such a foreign concept to be able to judge people based on gear. However our server quickly devolved into "LF1M GS 10k+ required!" and anyone who grouped with randoms had to install the addon. Anyone who claims that this LFG addon wouldn't disrupt play and that "you can just not use it" is delusional beyond belief.
And if you think that now Discord becomes "required" then you're the very crowd that made retail unbearable.