Several years ago, the Pages product team removed the Export Word Advanced Options capability allowing the export of the ancient .doc Word format from Pages. There is no existing Pages workaround to get .doc now.
If you are using Microsoft Word on the iPad, you could export from Pages as .docx, open in Word, and still save as .doc. Word v16.103.4 still supports this capability as well as converting a PDF exported from Pages back to a Word .docx document.
Unless you are attempting to input that .doc format into a word-processing application that is over 18 years old, most contempory applications support the modern .docx format and you should be using it. If the recipient is only reading the Pages document content, then export as PDF.
I hesitate to recommend exporting from Pages to RTF because some Pages document objects (e.g. equations) will export to separate files instead of remaining embedded in the RTF document.