Microsoft has enforced mandatory digital signatures for drivers, and getting a digital signing key from Microsoft costs a ton of money. So, presumably they do care.

In contrast, consider nProtect GameGuard, the anti-cheat system in Helldivers 2. It is a rootkit, and runs in the kernel. Why does Microsoft permit this? Shouldn't this be blocked? It must be using either an exploit like the article, or a properly signed driver. Either way, Microsoft could fix it -- by patching the exploit, or revoking the signing key.

The fact that Microsoft hasn't done anything about malicious anticheat rootkits is a sign that they really don't care. They just want their payment.