I originally came to Canada on IEC and then I applied for Express Entry - citizenship application is the first time I've had to mail a form to IRCC. So it is possible to enable applications to be done partially/completely online. There's even some forms where they can be validated by the applicant (there's a button in the form that checks all the entries and marks missing information). It's on the applicant filling in the form to make sure all checkboxes are marked but IRCC also have tools at their disposal to help the applicant.