I once got on a flight and the woman in the seat next to me had a massive handbag at her own feet and also a decent sized suitcase that she’d shoved under the seat in front of MINE
There must be a point where you’re thinking “this is a lot of stuff I’m carrying on here, bit ridiculous isn’t it?” I find it a bit annoying that airlines don’t enforce it better.
Even little things like waiting for a good few minutes for someone to finish trying endlessly to squeeze their massive bag into a tiny space in the overhead before you can get past them and get to your seat is pretty irksome
If it’s something you’d put in the luggage hold of a coach rather than carrying it on, then you should probably shouldn’t be carrying it onto a plane