Disclaimer: This is speculation based on my knowledge of Swedish. Don't quote me on this.
I recall reading something in the Swedish course about this. When making general statements like this, I think you're supposed to use the neuter form of the adjective. Italiensk mad is a pretty broad term; we're talking about all Italian food here, so we use godt. If it were Den italienske mad er rigtig god, when we wouldn't use it, because we're being more specific. I hope that makes some sense... it seems like a really weird concept to me, but that's what I learned. I think it works that way in Swedish, so I assume it is true here, too.
due to my little knowledge of german .. "virkelig" means "really" and "rigtig" means literally "right", in danish i believe that both have the same meaning it's just about the context and when shoud you use each one ... I'm not sure but I hope that this could help you somehow !
I was really confused by this as I thought the adjectives should not have taken a final -t as mad is common gender word. I asked the Duolingo Danish Facebook group and got the answer (such a good group)!
Seems the neuter form (add a -t) of an adjective is used when the noun is abstract, collective, or general. So as mad is food in general, the adjectives should be rigtigt godt. Duolingo wins again!