The popular narrative seems to be that United, Delta, and American ‘eliminating change fees’ hurts Southwest Airlines. Southwest hasn’t had change fees, and this takes away one of Southwest’s advantages.
Other airlines still have their advantages over Southwest, from premium cabins to lounges, but those are the same as before. What’s different in the new environment is a growing cost advantage for Southwest, and most people misunderstand what ‘no change fees’ on United, Delta, and American means anyway.