The full flash intro page is only a relic because Apple dropped support for Flash. Now, so many designers have a full page video that play, and prevent text from loading until every bit of bloated JavaScript finishing downloading and executing.
It's a different package, but it's the same junk.
My biggest pet peeve these days is a Nav Bar that takes up too much vertical space and follows when I scroll. Usually these are mobile-first designs, but especially on phone when I rotate to view more horizontal content using iPhone 13 I’ve got like two text lines visible!
I despise the full-background, 4K video pages.
Makes connecting from bad cells a royal pain.
But some of the dependency libraries can be almost as bad.
I don't like 1MB pages, so a button can be animated.