See https://www.w3fools.com/ for some of the complaints folks have/had.
The front page now says:
Today, W3Schools has largely resolved these issues and addressed the majority of the undersigned developers' concerns. For many beginners, W3Schools has structured tutorials and playgrounds that offer a decent learning experience.
> Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.