I snorted when I saw Vegeta remind Goku that they couldn't breathe in space and they had to stay on-planet like children while Moro fought the Grand Supreme Kai and Merus. You'd think since the issue was brought up they would have developed a technique or even resorted to asking Bulma to make some sort of tech to help them fight in space but nope.
Despite countless years of training and fighting increasingly powerful opponents...the Freeza that destroyed their homeworld and entire race nearly 50 years prior could camp in space and destroy everything they care about, including them, with a single well-placed Death Beam at night when they're fast asleep. Gohan Beast, Ultra Instinct Goku, Ultra Ego Vegeta, The Legendary Broly? They could all die to the power of 530,000 that blew up Planet Vegeta when they go to sleep and Freeza takes the shot.
To me it's just pretty pathetic. Normally limits like that can make for better writing (Most mainstream anime example being JoJo) but their inability to survive in space just means other characters need to be dumber, chaotic or have some sort of sense of pride that stops them from just doing it. Not to mention it horribly limits the variety of action, we could have Goku blitzing through the universe busting through planets and stars against Beerus, Freeza, Broly, etc but that one weakness makes that impossible.
tl;dr - Saiyans are dumb and nonthreatening when they can't survive in space.