Extended producer responsibility (EPR) is a key policy principle to mitigate adverse effects of plastic pollution, holding producers accountable for their products' end-of-life management. Yet, assessment of EPR effectiveness is limited by data quality and causal research design for post-hoc analysis, especially with regard to analyzing country contexts. To grasp EPR's true impact, it is crucial to consider its broader regulatory, socio-economic, and value chain contexts. We introduce a refined ex-ante framework for evaluating potential effectiveness of EPR based on scope, design, and context. To test this approach, we apply the framework to Belgium, France, and Germany and find that all three show high effectiveness, albeit Germany ranks highest. Germany is strong in technology, recycling options and routes, but lacks transparency. Belgium and France grant municipalities greater influence yet face impending cost escalations. Our findings also underscore the need for EU-wide harmonization of several EPR design and implementation criteria.