Oh, yes, BW is right. I am a MANIAC when it comes to my parrots food and even I don't change their diet (unless it's truly awful -like the cheapest seed mix or the colored pellets- or the bird is sick from it -as in fatty liver or kidney damage) at the beginning. I always offer them the same thing I give all the others and at the same time the others get it (because a strict solar schedule and the daily routine is one thing that I do from day one) BUT, at the beginning, I also give them what they were used to eating in their previous home. Been rehomed is hard enough on them and one doesn't want to add to the stress (that's another thing that I am a maniac about: stress) by giving them food they don't even recognize as such.
And, yes, again, on the not everybody having the time to do all the research that is needed to begin to scratch the surface of the necessary knowledge (it's hard, it's complicated and, so far, it seems to be never ending!). Thankfully, you don't have to start from square one (as we, people who started having parrots over 20 years ago, had to do) because there is now plenty of information on the net to put you on the right track and all you have to do is take it from there. I only have one advice to you on this: always go to their natural diet (Nature always knows best) and never take anybody's word for anything, just use their opinion to do your own research on the subject.