A potential solution for issues with users gaining unpaid access to premium content by blocking JavaScript or using browser extensions would be to adjust the paywall in such a way, that the content of the articles will be loaded only after a server-side access check so that client-side plugins cannot block the script and reveal the "premium" content.
Below is a summary of 3 different client-side paywall implementation approaches and the relative security and user experience tradeoffs.
The rightmost option is the one, where the content on the page is loaded only after the access check of the user was successful.