Weber's ideas are relevant in two ways today.
First, they can still be used (if one is persuaded by them) to explain some of the differences between "North" countries and "South" countries. It is still true that predominantly Protestant countries (Germany, the UK, the United States) are better off than predominantly Catholic countries (Spain, Portugal, Mexico). Weber's idea might be used to account, in part, for this phenomenon.
Second, the basic assumption that underlies Weber's idea can still have relevance. This is the assumption that a society's culture affects the degree to which it can succeed economically. This assumption can be used to help explain why, for example, countries like Japan and Singapore have become more advanced than countries like Indonesia or Vietnam. We can use Weber's assumption to argue that their culture (even if it is not exactly Protestant) has values that encourage capitalism while other societies' cultures do not have such values.