You are correct that it would not instantly become unusable. But when all editors with integrity have ceased to contribute in frustration, wikipedia would eventually become stale, or very unreliable.

Also there is nothing stopping a person from using an llm to summarize an article for them. And the added benefit to that is that the energy and reasources used for that would be only used on the people that wanted to, not on evey single page view. I would assume the enegy consumption on that, would be significant.