But given that, how do we move forward? We shouldn't be stuck in the past forever. We shouldn't probably even be stuck in 2013, when IE11 was released. If their site requires heavy client-side code, and if they want to build it in a fast and reliable way, they have almost no other choice but to think of frameworks.
Wikipedia is essentially a public utility now. It's not their responsibility to move technology forward by forcing their users to upgrade their machines. There's loads of other players that do that already.
> If their site requires heavy client-side code
It doesn't.
The beauty of the internet is that any website is free to decide as they see fit - if they don't want to support IE/Edge/etc then that is their choice.
No website is a 'public utility' bound by laws which dictate what browsers must be supported - that remains a free and open decision.
IE11 is a dead browser, and the sooner it breaks for good, the better.
Wikipedia at the very least has the editor for all those documents.