Well, nowadays, you can implement a lot of logic for forms using HTML and pure CSS, without JS at all. Example:

  form:has(.conditional-checkbox:not(:checked)) .optional-part-of-form {
    display: none;
  }

I’m not saying it’s better (it’s not). Just saying there’s a lot of space between “just HTML” and “a web framework”. It’s worth considering these other options instead of going “full React” from the get-go.