This is a pretty succinct way to say it. Sure, champions are meant to be strong at certain things (and should be weak at other things too, Caitlyn), but ultimately this is a multiplayer game, and champions should be interactive as well as on theme. Caitlyn's traps are on theme, but are not interactive in many situations: in the laning phase, for example, even three traps can be an issue, because during that time it's not really possible for the laner to flank her or use an alternative route. Walling off an entire lane later on, particularly at choke points like the inhibitor turret, can be countered by dashing over the base walls, but that's counterplay reserved to mobile, survivable champions. The alternative is to push another lane, but that takes time and gives Caitlyn the opportunity to redeploy her traps. Effectively, the net result is that they remove interaction from the game and give players fewer options, instead of posing a challenge that can be overcome with unique tactics. The fact that the traps are indestructible until stepped on means taking the time to dismantle them isn't even an option either.
More generally, features in a video game should only be frustrating if they can be reasonably overcome. If a champion is frustrating because they have more reach than you, but suffer when attacked from an unpredictable angle, that's alright because there is a means of overcoming that frustration. If a champion has one really reliable effect, but is especially unreliable elsewhere, they'll be frustrating at times and easy to deal with at others, but will feel outplayable, so dealing with the frustration they present is a matter of adapting your play to the champion. When a champion outputs a lot of frustrating power, but doesn't feel like they can really get punished for it, that's when things turn bad, as is the case for Caitlyn and a few other champions in particular.