quartic, Monarch have ordered the 737 MAX, which will have the 'sky interior' (the same as the 787, which has proven to be a success with PAX). Even 737NG's have the option of having the sky interior installed, RYR just don't buy that option.
Maybe you should book a ticket on a Norwegian or Thomson 737 and have a look for yourself before you accuse Monarch management of ordering the wrong airplane, based on your perceived views of its Cabin.
they do know which is most comfortable with wider seats, easier overhead stowage and better ambience
Seat width between the two types is almost identical, the overhead bins on the 'sky interior' are bigger, easier to use and create a wider cabin to stand up in, and mood lighting comes as standard.
Back on topic,
Monarch was a career airline 10 years ago, its recent history has shown nothing but poor results despite continued investment. Its latest expansion was a 'go big or go home' move, and many pilots recognised that and didn't apply for that very reason.
It seems the gamble they took is not going to pay off, Monarch is actively positioning itself as a small scheduled airline, and that model has proven time and time again not to work in modern aviation. I wish everyone at Monarch all the best, it was an airline I always wanted to fly for, it may continue to plod along for another 5 years however I think the best outcome now will be a merger. But realistically that is also unlikely.