QT is a personal choice. I can't remember the last time I QT'd a fish (it's probably been 15+ years) except for a very few specific cases where there was clearly an issue. I also can't remember the last time I lost a fish to disease or parasite. I don't think I ever have, actually.
Instead of QT, I try to plan carefully when and how I add fish, and only get them from known good sources. Less work for me, less stress on the fish, I'm supporting good businesses and/or other hobbyists; everyone wins. We drill it in to newbs that they shouldn't ever put fish in a new, sterile, unestablished tank, and then we basically tell them to do exactly that in a quarantine tank, and try to pass it off as beneficial. I don't get it, honestly.
But we don't need to derail this thread. Mandarins are beautiful, I'm happy that ORA and others are breeding and hopefully we will reach a point where captive bred fish that are taking prepared food are the norm, and everyone can reclassify this species as the OP seems to be suggesting. I agree with Ron that the "expert" rating is appropriate, for the majority of Mandarins. I've cultured food in the past. It's a fun experiment, but I don't think I'd ever want to depend on it to keep a fish alive. That said, I plan on eventually getting a Mandarin for my 24g cube, as soon as I can find an established individual who's eagerly taking prepared food.
