Am I the only one who gets really upset to hear this term constantly throughout the day in conversations when someone means “that’s horrible”?
You aren’t the only one to think of the phrase that way - but I also think lots of people don’t have that connotation.
I remember being a teen and using that phrase. My grandmother finally said something to me about how it was inappropriate because of “what it comes from”. I was
really confused, since I honestly had no idea what she was talking about and didn’t even know about oral sex (and she refused to explain it to me - but got very upset that I wouldn’t admit I already knew something I really didn’t know, LOL). For me, saying that something “sucks” just meant “it is draining, it sucks a little joy and happiness from your life”. It made intuitive sense without having some other meaning, so I was pretty surprised when I finally did learn about its other meaning.
I probably do still use the phrase - I find it communicates how I react to bad stuff better than “that stinks”. I find bad stuff draining, like a hole that needs to be filled in, and generally try to “fill in” that “sucked-out space” with something else good - like a prayer. I don’t find bad stuff generally permeates the air around me like a stench that I can only ignore and can’t do anything else about, though, so “it stinks” seems . . . somehow wrong, overly passive and pessimistic.
I also work in a casual, male-dominated environment where the occasional cuss- or curse-word isn’t rare. It’s part of the trade-off for being able to focus on work rather than looking good - sometimes your coworkers don’t bother to make themselves look good

So saying that something “sucks” is so mild that no one would think anything of it, and the f-word even wouldn’t really turn a head (unless said in front of a pregnant woman wearing a cross necklace . . . LOL, I find it rather amusing when people try to change their habits to make me comfortable since I’m really quite used to it, although I do also appreciate the thoughtfulness).
If I was actually bothered by the phrase “that sucks”, I would probably say something to the people I talk to frequently - husband, children, close friends - for my own comfort, so they would know that I find that phrase discomfitting. If someone said something to me, I would apologize and explain that I just mean that something sounded “draining”, then would attempt to avoid using the phrase around them in the future.