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And pointing out the recent blockage incident as a case against megaships isn't a great argument either. Imagine the incident had never occurred, but that someone started campaigning for constructing a wider and deeper Suez canal in order to save X tonnes of fossil fuel a year by allowing more fuel efficient ships to pass safely, wouldn't we all be in favour of it?

What snotter said:

Using less fossil fuel per whatever (tonnes shipped) isn't always the same as using less fossil fuels, especially if you end up shipping more tonnes or whatever is applicable to a situation where more efficient use of a fossil fuel is being discussed.

Simply put, larger and larger ships are a symptom of a larger and larger shipping industry--because there are numerous perverse incentives to over-concentration of the economy--making things where not nearly as many of them are needed and then shipping them all over the world. It's mainly subsidised by artificially-suppressed transport costs. Getting rid of megaships, in turn, would be a symptom of a shipping industry growing smaller, and overall fuel use would go down. It's not a question of comparing individual ships and their individual fuel use. They're all tied into their wider context of how the underlying economics work.

(And, for the record, ships like the Ever Given, while ridiculously large, are by no means the only ridiculously large ships--even much smaller ships are still way too large, whether you're talking about cruise ships, oil tankers, or container ships.)