Hi there, this is Marc. Thanks for reaching out to the community.
You have multiple authentication methods enabled on your Microsoft account and it's defaulting to the newer sign-in experience. Go to https://account.microsoft.com/security and sign in. Under "Sign-in options" remove PIN and Windows Hello (facial recognition) if you don't want them. Also turn off "Passwordless account" if it's enabled.
The "stay signed in" prompt is a security feature that's now standard, you can't disable it. Just check "Don't show this again" and it'll remember your preference for that browser.
If you're still getting the method selection screen after removing those options, clear your browser's stored credentials for login.live.com and outlook.live.com, then sign in fresh.
The old simple login flow isn't coming back, Microsoft pushed everyone to the unified sign-in experience. This is as simple as it gets now.
Best regards,