We still have blind pick to cater to vastly more ignorant toxicity, and it has more issues than team builder ever did.
If my options are "fast queue times in a queue that almost guarantees a toxic experience" or "long queue times in a mode that guarantees that at the very least everyone is playing exactly what they want to", I pick the latter every time.
Team Builder had a role. It had a purpose.
Blind pick does not and never has except to cater to people who either A) Are so impatient that they're probably the types who queue for a game when they only have 10 minutes to play and then leave, or B) Are impatient AND want to try to instalok and will usually fight tooth and nail with their own team for not getting what they want (because it's usually mid yasuo or some other player who knows they can't get their cancer-inducing champ in draft).
Especially now after the new champ select is pretty robust. I really don't play blind pick very often (usually when I'm dragged into it cuz a friend invites me into his other friend's room or something), but literally nearly every game has a boatload of toxicity because of the way blind pick functions.
Team Builder at least removed one of the core frustrations for players: Being locked into a 20min-1hr long game playing a role/champion you did not want to play. That alone removed a lot of toxic experiences, at least in my own anecdotal experience with Team Builder.
Plus it meant you didn't have to deal with flaming if you, for example, DID want to play the new champion, or needed a 5th for a weird team composition: Everyone knew what they were getting into when they got in the room, and had the chance to opt out.
While it existed, I played Team Builder almost exclusively. Again, anecdotal, but I have no clue where these claims of it being "difficult" to get into a Team Builder game for reasons of too many hosts/joiners or something comes from, as that was never my personal experience and I played a lot of League back then. In fact I partially blame TB's removal for my lessened interest over time as I've been playing so long that when I feel like playing League, it's often cuz I'm in the mood to play a certain champ/role/build, which Team Builder guaranteed.
Sure, it always had long queue times, but if you're expecting short waits, play Draft. If you're expecting like, shorter than 2 minute waits, you SERIOUSLY need to see a specialist about potential ADHD or a life coach about your unrealistic expectations for the universe. If you can't afford to wait up to 5 minutes for something (Draft Queues for most people), you either do not have time and shouldn't queue or need to learn some basic patience. Team Builder offered the benefit of "hey, if you're willing to wait 10+ minutes to play a specific thing, here's where you go".
Sure it definitely had FRINGE cases of like hour long waits, but (and again, my and my friends personal experiences) usually those were either attributed to you expecting something generally unreasonable, like day 1 playing the new champ or wanting to do some crazy 3 bot team composition or something. They certainly were not the norm despite what naysayers like to claim.
Team Builder served a unique function not provided by the other modes.
Blind Pick does absolutely nothing except serve as a festering cesspool for toxic experiences, and pretty much has since the game's release.