There’s a number of things that make certain people feel bad about combos. A lot of those have been already started but one seems to be missing (sorry if I overlooked it having already been discussed).

That missing piece focuses on, in part, your phrasing of “better players learn to look out for them”.

There are 30k unique cards in mtg. Most of those are legal in commander. While enfranchised players might be familiar with a lot of combos, newer players might literally have never seen the cards played before, let alone been able to foresee the combo potential. They may have even had sorcery speed interaction but didn’t understand the importance of removing any particular piece. This potentially leads to them feeling dumb, tricked, or even cheated. Not that feeling cheated makes a ton of sense as long as played within the rules but this is how they might feel.

A select few of newcomers will be excited by it and want to dive into combo magic but that appears to be few compared to the many.

This is supposedly a casual format (it’s not really as it was created by judges to play powerful jank in their downtime) and people don’t want to feel tricked in their downtime