How to calculate whether a rating is good

I have seen many forums discussing whether a rating is “good” or “bad”. Personally I feel it is satisfying when ur rating climbs, like how my other acc rating climbed ten times from 100 elo. However I disagree with how other people define ratings.

Firstly, not everyone learns chess with a coach. Lets say person A and B both start at the rating of 400. However, person A has a chess coach, and thus able to learn things like basic openings and principles, endgame techniques, tactics and strategy. His rating might climb to 1200 within a few months, while Person B does not have a chess coach and learns things the hard way, like not blundering after losing games. Maybe in the same period of time as Person A he gains 50 elo? Can we say that person A is a genius while B has a low iq? No.   Like me before i had a chess coach, i  gained perhaps 200 elo in 5 months, but after receiving proper training, my rating spiked. 
Therefore placing certain ratings in different category are not really reliable. 
If u disagree comment down below on why. I would like to hear ur opinion on this matter.