Whether you like DQ or not, you are still playing in a single queue when you want to play ranked.
True. And that's what a portion of the fanbase has a problem with. If you keep Dynamic queue and do not give an option for people who want to avoid premades in their games, you have a portion of your game population that is permanently dissatisfied (and there are plenty of good reasons why people do not want premades in their games when they are playing solo). If you get rid of Dynamic queue to appease them, you have another portion of your game population that is dissatisfied (people that hate solo queue, and want to climb with friends).
Actually, you might be wrong here. Lets assume that half the population hates DQ, that means with a SoloQ option, your wait times would double. If it normally takes 5 minutes to get a game, it would now take 10.
I've waited up until 8 minutes to get into a game a few times. 10 minutes may seem like a lot, but not when you've got another browser open, doing something in the background. But this one is a matter of opinion, some people can't stand waiting. To me, waiting a bit to get into game is the least of one's worries, since the games last half an hour to close to an hour anyway.