CPA marketing still works and will always work. The best way nowadays in my opinion is to use paid methods for promotion. And with paid methods, the campaign setups need to be proper in order to have maximum conversions at minimum costs, landing page (where applicable) also must be optimized towards having maximum conversions possible. In my opinion and experience the best CPA niches revolve around finance (make money, earn money), health (keto, nutra, beauty) and relationships (dating), casino (gambling).