Fundamentally, maintaining MDN is costly because of the rate of instability in rapidly changing browser APIs. Those APIs change quickly and inconsistently because they’re managed by a centralized cabal of a few corporations with a combined multiple trillions of dollars in market cap. And yet, somehow it’s Mozilla, the browser vendor with the least money, that ends up saddling the cost for MDN. Why is this?
In general, Big Tech companies should pay more into open source, and especially into the standards committees they manipulate to their own ends. Perhaps there should be some kind of NATO-like membership fee based on percent of global revenue. It would be amusing to see w3c tax these corporations more efficiently than any government has been able to.