I understand attempting to load the YouTube.com website is redirecting to kidsYouTube.com which you don't want.
YouTube is a Google product so the account information it's alluding to is probably a factor. You would need to investigate that separately. Perhaps it concluded you're too young to view the content you're seeking, and the reason may have something to do with the information in that account.
If that doesn't explain it try clearing Safari's history and / or website data (cookies):
Clear your browsing history in Safari on Mac - Apple Support
Clear cookies in Safari on Mac - Apple Support
If Safari doesn't open a page or work as expected on your Mac offers many additional suggestions. It's very comprehensive but you have to exhaust all of them.