Each format has strengths and weaknesses. Both team-builder (TB) and something like draft both use MMR, logically, and for the purpose of rounding out even matches. The only thing TB lacks in this process is pool size (because the majority avoid the concept) and time (balancing out new MMR's). Each of these concerns are easily rectifiable, i.e. more players and time.
The benefits of draft is a faster queue time and... well... that's the only strictly factual benefit to draft. Other than it reflects professional play more accurately.
The benefits of team-builder is that, if used, reduces trolling, arguing over positions and placing a player in weak/new position. How many times does the lobby open up in draft to have one of these three factors take place? How many times have they alone lost you a game and/or ruined the experience?
How many well written Reddit posts include queue'ing up at certain times to avoid trolling, or arduously attempting to control the lobby chat to maximize team potential by placing them in the right roles to maximize your chances of success? Doesn't TB address all of this?
In either case, those who choose the formats do so because to them the benefits outweigh risks. So far, players seem much more willing to get a decreased queue time at the cost of dis-satisfactory, yet easily rectifiable issues. Those who chosse team-builder want to play champ A, in lane B, and avoid trolls of Ahri support. They want to avoid someone not typing faster enough, or logging in half a second later than someone else who is typing "mid" like a squirrel on crack, insta-locking a mid champ only to end up with two mids?
In the end, pool size is something that can be solved in team-builder, and the MMR analysis isn't weak, it's sound. In the end, you are just making a choice. Do you want longer wait times, and more scrupulous team leaders (looking to actually win and avoid trolls), or do you want 5 random people thrown into a lobby to duke it out in chat?
The choice is yours. So far, I play both. I do avoid TB because of queue times, but when I want to play champ A, in lane B, and avoid trolls, I put in the extra minutes and have yet to be dissatisfied. The only real thing you lose in TB is the professional method of drafting, which in the end nobody does very well imo. When I want to play that level of game, I play ranked, which I also enjoy (but comes with its necessary evils).
That has at least been my experience.