Designing an e-learning system or any system shouldn't just depend on the language or framework you are using.
Well anyway I am curious how you can design an e-learning system that's accessible to mostly everyone using one language only. I can think already you will be using at least JAVASCRIPT on the frontend. So if it's just one language, then you are automatically saying your backend is NODEJS
If you will go with Flask or Laravel (Python/Php), are you planning to write the frontend on these languages? I think you are severely limiting your options. I am not talking about server side rendering templates.
If you need to provide videos, interactivity, charts, games on the frontend, these will be mostly written in JavaScript (well let's exclude Flash coz that's dead but technically it uses ActionScript which is a cousin of JavaScript)