If the queue times are longer for dynamic, then that reflects that a significant percent of the community doesn't care for dynamic mode ("75/25"). So you want the 75% of the community who wants to play solo-queue to have to play in dynamic so the minority 4-man groups have a quicker queue? That to me is very selfish.
For people who want to play dynamic, they might take a hit in the form of longer queue times, but they still get to play the mode they want with any amount of friends.
For people who want to play solo, the option is just gone? Never again can you play the mode which made you love this game for over 6 years because the new dynamic queuers will have a longer queue time?
I started this game over 6 years ago because a bunch of friends from my WoW guild wanted to play LoL. Even though many of the still play, I quickly found out I enjoyed solo-queue over group queue and to date have played maybe 5 or so ranked 5's in a 6+ year career. I have however played ~10,000 solo-queue games and when they announced a dynamic-only mode my stomach sank. I was fully intent on quitting LoL finally and simply watching LCS but now I have an excitement for the game I haven't had in years with the new pure solo-queue option.

All this is just to say that you have to respect that a lot of people really hated this change as it would cost them their favorite aspect of playing this game. Just imagine if the game was dynamic queue this entire time where plenty of people played solo but some desired a solo-only option, then Riot announces a new game mode: Solo-Queue which isn't a separate game mode but the only game mode. Goodbye all you people who preferred grouping with friends for ranked right? Empathy man!