You can make a good living off of fixed price games - micro-transactions have only become popular in the past 5 years or so (at least in the US). The game industry was very profitable long before micro-transactions. Does not matter if you are doing mobile, PC, etc. You probably will not make as much money, but you at least can feel guilt-free about your work (if micro-transactions do make you feel guilty). Many fixed-price games have made millions of dollars on mobile (for games that cost a few hundred thousand to produce, at most).
All that said, I am not against micro-transactions. I am against them when there is no other reasonable way to play the game though, or they are psychologically manipulative. I have probably spent a few hundred dollars on micro-transactions, and the experience left me feeling empty (not unlike a washed up drug addict)...which is why I refuse to buy any more games that use this method in an exploitive manner.