Interesting to hear this as I haven't heard anyone refer to their breeding behavior as super aggressive. I am planning on a breeding pair for my office tank but they would be the only inhabitants.
Depends a lot on the individuals and ime tank size is a factor. I've had several breeding pairs, none of which were especially aggressive toward other tankmates. Protective of their spawning site, eggs, or fry, sure, but no real harm to the other fish.
Tank size makes a difference with sevs ime. I've seen several examples of them being nasty in smaller tanks where they feel crowded. In fact, I bought a wild rotkeil once that killed off anything they tried to put in the same tank (20 gal). Was a perfect citizen for me in the various 4-6 ft tanks I kept it in over the years I had him.
Not to say you can't get a mean one or a more aggressive pair or that someone else can't have a different experience, but it's not a rule that you can't keep pairs with other fish, at least in a large enough tank.