Full filler episodes might not exist but one piece episodes are still 50% filler.

Are anime-original episodes considered filler too? Because the last episode of Makeine is anime-original, though the author wrote the story.

And there's also The Promised Neverland S2 and Wonder Egg Priority, from what I remember.

There aren't usually whole filler episodes anymore but there's a lot of weird fluff in Demon Slayer that wasn't in the manga.