AI will indeed kill the leetcode interview - because once it replaces human SWEs you don't really need to give leetcode-style brainteasers to any human anymore.
Not defending it but I think it was more of a test if you have the dedication (and general smarts) to grind them for a few months than software engineering skills.
Similar to hiring good students from famous universities even if most of CS isn't that applicable to day to day programming work, just because it's a signal that they're smart and managed to get through a difficult course.
