The usual advice about character classes is only for casual users who don't know what makes a secure password. Entropy is the deciding factor: Ten random lower case letters is much more secure than "Summer2024!", which satisfies most password rules and has more characters.
Personally I stick to lower case letters for things like my Netflix password or Wifi key, because typing with a TV remote can be a huge pain. To keep a similar entropy, just increase the length by one or two characters.