I don't know why you got that impression. Warfarin is still widely used and still the most popular rodenticide in the world. It's even still commonly used in Canada AFAIK:

https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports-publications/pesticides-pest-management/fact-sheets-other-resources/rodenticides-agricultural-settings/questions-answers.html

https://spca.bc.ca/ways-to-help/take-action/urban-wildlife/humane-rodent-control/rodenticides/

https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports-publications/pesticides-pest-management/fact-sheets-other-resources/rodenticides-agricultural-settings.html