Look at the queue times if you want to see what mode is played more.
The number of people playing H.A. is far more than playing ranked.
The number playing anything is more than playing ranked.
How can you tell? Queue times. If there were that many people playing ranked, it would have the shortest queue times, not the longest. Riot would not have to work at trying to make queue times shorter. So stop going on about ranked being the "competitive" mode. It is the unimportant mode. The game would be better off without it.
Then riot would be stuck with doing real balance for all the rest of the modes. Making the modes that real people play all the time more fun.
The rift is NOT where competitive play happens ... it happens everywhere in a game. Every mode. Even if coop vs A.I. The people that play, are playing a game (even in ranked). None of the modes are "serious" they are all "just for fun" ... it is a game. So drop the attitude that any mode is more than any other. It is false pride.
Ranked is far less popular because it appeals only to those that need external affirmation of their value. How do you know it is far less popular? Because of queue times. If there were thousands of people lining up to play ranked, the queue times would be seconds, not minutes.