I've had these before and also thought they were kind of blah.

I have one more tip for you: After you defrost the shrimp, lay them out on a paper towel. Pat them dry with another paper towel.

If you saute wet shrimp, it tends to get soggy and it just kind of steams in the water.

They smell terrible

Argentinian red shrimp are cheap because they're not very good. Not a lot of taste, way too much waste to be deveined, subject to turn to mush when overcooked (as opposed to tightening like white shrimp). Stick to shrimp from the gulf or the Carolinas. Same goes for crabmeat from Vietnam or South America. Tasteless.

Yes, add salt. Maybe some Italian seasoning. Probably more garlic than you used.

OP here with an update. It took me a month to work up the courage to try to cook this. I put six shrimp in a ziplock and put the ziplock in a bowl of water. I was told a half hour, but it definitely took 50 minutes to defrost. I melted butter on a medium low heat while fettucine was boiling. When the pasta had six minutes left, I dumped the shrimp in the pan, turned the heat up to medium, and sprinkled minced garlic in. After three minutes I turned the shrimp. At six minutes, I honestly couldn't tell if they were done, but everything I read said five minutes so hoped for the best and took them out of the pan.

They were ... not great. Just meh. Maybe butter and garlic weren't enough? Maybe salt? I don't know. They weren't bad, just kind of boring tasting. No idea whether or not I ate raw shrimp, but based on the time, I shouldn't have. They seemed to be the same color as when they went in but I'm not good at seeing stuff like that.