I was in the same boat as you. I despised underroasted sour shots. I found that there is only one way for me to enjoy high elevation, single origin, light roasted espresso. 30g espresso to 80g hot water. Pull your shot then add hot water to mimick a brewed coffee. Some of these are amazing.
When going to many "specialty coffee" shops here in NY state, I have found that none of these 17 year old kids even know how to use an espresso machine. It gets left on the same grind setting as the beans stale and they are told "fill this", "tamp down", "press button". One girl was tamping while holding the portafilter in the air
The results are always underextracted shots that gush out at an alarming rate and taste like dog shoooot. Not to mention the machines in some cafes are never cleaned, at least not the inner parts that touch the coffee and water...including portafilters.
Do yourself a favor and give one last chance to my method above. One notch back from bitter should do it. You want zero bitter. Also let the coffee get a little warmer than room temp after brewing before sipping and think of it as a summer time coffee.
For the good Italian shots, not much beats Caffe Lusso Gran Miscela Carmo