Each piece that becomes MIT means less pressure on corporate users to give back any changes they make, and we'll end back up in the 1980s again where "Amazon Linux" is full of secret-sauce they refuse to publish and makes the base system incompatible with "Google Linux" (or whatever happens to be kicking about), creating deliberate lock-in out of a system that started open. In much the same way that macOS and FreeBSD are divergent today.
That would be an awfully awkward move in the realm of Linux-related politics but if having an MIT-licensed coreutils was such an existential thread, at least you can fix it with aggressive license moves and not code.
I am not totally sure I see the actual concern here, that a company is going to sell devices with a really great `find` implementation but not contribute it upstream?
What it meant was a headache for writing platform-agnostic software. It was not a productive way to create software.
Replacing GPL software with MIT software just encourages this behaviour to come back. We already see it with how macOS userland took FreeBSD and sprinkled incompatibilities everywhere.