Does mono audio change the music quality alot?

I actually feel like a idiot listening to music on mono on iphone for the past 4 years. I got new iems today and I realized through some left and right video tests that my iems didnt work as normal. So I checked out the settings to find mono audio on and turned it off and went into a world of immersion. Before this I have been trying out alot of iems to see which ones good for music, without turning off mono. I didnt like most of them but now I look back maybe I would have liked them if the setting was turned off. Does it really affect alot of iems sound quality alot?