Your guess is as good as mine, honestly. As for Teambuilder, it was pretty cool. Basically you could opt to queue up as a specific champion in a specific role and then select what roles you wanted to have on your team. So you didn't necessarily have to have a Jungler; you could opt to have a second top laner instead. Or you could opt not to have an ADC at all and queue with two supports as your preferred team make up. The queue timers could be lengthy for that(20 minutes was pushing it but it could easily happen) but you had a lot more freedom over who you played with. Similarly, if you wanted to play an off meta thing, you could queue for it and it could be a sort of warning for people on your team; they would know before champ select that this is what you were going to play and they could kick you before then. It was great for weeding out trolls or toxic people or, if you just didn't feel like playing with an off meta player, you could opt not to have one. Games were a lot less toxic as well.
Really a shame that you couldn't have been here for Teambuilder. It was pretty awesome. It also gave you cool icons for free if you played a certain role enough times. Oh!! And it used to see that you were new to a champion and would attempt to queue you up against other people who were also new to their champion so it was easier to learn them. I almost forgot about that. Teambuilder was AWESOME and had a lot of great things about it that... just don't exist in the current game anymore. :( They could honestly get rid of either blind pick(which sucks) or ranked flex and put in teambuilder instead and I would at least be 100% happier.