It's very cool that you are sensitive to how frustrating saying "that sucks" is for you. Many people are looking for just that, though. It might be informative

It's very cool that you are sensitive to how frustrating saying "that sucks" is for you. Many people are looking for just that, though. It might be informative to try out "that sucks" enough times to see what response it gets from the person you're interacting with. You might be surprised. (I was.)