Really? The total time period for migrating the account was something like 3 years, they sent emails reminding you about it, and mentioned it in the launcher. I don't know what else they could have been expected to do?

They couldn't just "migrate everyone's accounts" because there's no obvious way to do that. Simple example: Let's say you bought Minecraft for yourself and your two kids so you could play together. These were little kids, and Mojang accounts aren't uniquely tied to an email address so they all have the same email address. MS accounts use email address as username. Without asking the user, which of the three accounts gets tied to that email address, and what happens to the other two? What about cases where the Mojang account is for an email address that doesn't have a Microsoft account? What if it already does, but the email address on the Mojang account is an older email they no longer use or even have access to and just never bothered to update because the email on your Mojang account was only really relevant to recover your password? Etc, etc, etc.