I think a part of it is the difference to losing to something “reasonable” vs “unreasonable.”
If you’re clearly really bad at the game when we are in a fight with line of sight but somehow you keep picking off my teammates through walls… That’s the kind of thing where cheating really starts to get annoying.
You may still be on the same skill level overall, but for specific parts of the game they have super powers, and it just feels ridiculous.
Smurfing is also a real issue because cheaters seem to overlap with trolls that just want everyone else to have a bad time, so they’ll spend a bunch of time down ranking, so they can spend a little time giving a lot of players a bad day.