You are mixing up real mythic raiders that race for world/server firsts , maybe top 50-100 guilds (these guys don't really bitch about the change, mostly they do not care) and wannabe "mythic raiders" as they call themselves, often featured with corrupt/egocentric leadership, yes they can still do some mythic content, they can even give out loot nobody else needs to trials (but of course never tf or bis trinkets). And they keep recruiting them because of toxicity, members abuse, poor planning or 100 other reasons. You might say it's not about your guild, ok, but there's plenty of those and now the issue has been addressed.Mythic raiders are not going to forget that they used to be able to assign loot properly when every week you're going to have loot dropping that is going in the wrong place and can't be traded, and any item that DOES drop and can be traded requires a huge hassle of trading it around post-kill, slowing down the raid instead of having the master looter sort it out while the rest of the raid gets on with the next trash pack.
The only people who will forget about master looter are the kind of people who never needed it in the first place, and aren't the people who are asking for it to remain - ie; mythic raiders. No one is asking for ML to be global, but making it not function in mythic raids is almost as idiotic as your claims it will be forgotten or that only toxic guilds will care.
You have no idea what you're talking about, I don't understand why you post about the topic when you're completely unaffected.