Hi Bluss,
What is happening is that Minecraft is still cached to an old Microsoft account on your device, so even when you try to sign in, it automatically redirects you to that account instead of letting you choose a different one. This is a local sign-in and credential caching issue, not a problem with Minecraft or your current Microsoft account.
Minecraft uses the Windows account store and Xbox services to remember the last account that was used. If that account is no longer accessible, the app will continue trying to authenticate with it until the cached credentials are removed.
The way to resolve this is to fully sign out and clear the stored Microsoft/Xbox credentials, then sign in again with the correct account. You can do this by signing out of the Microsoft Store, Xbox app, and Xbox services, and removing the old account from Windows if it is still listed under Accounts. In some cases, resetting or reinstalling Minecraft after signing out of all Microsoft/Xbox services is necessary so it can prompt you to choose a different account.
Once the cached credentials are cleared, Minecraft will allow you to select and sign in with your current Microsoft account normally.