There are long forms, and then there are massive forms. A form with over a hundred fields is a different beast because you can't divide them into pages and call it a day. Additional UX techniques are necessary to make the form faster and easier to complete.
For instance, this loan application form contains 104 fields on one page. Splitting the fields into several pages is only the first step. Then, you must make it easy for users to navigate the pages, save their progress, and track it.