Patrick Mahomes, Josh Allen, Justin Herbert just to name a few more - they were all lauded for their elite athletic gifts, cannons for arms and mobility out of the pocket, but they were deemed raw. They needed to improve their mechanics to become more accurate, their ability to read defenses and how they dealt with pressure.
What numerous NFL teams failed to recognize is that those aforementioned “flaws” are all coachable. It could take a few years, it certainly did for Mahomes and Allen, but once it clicks, a Hall of Fame trajectory can be seen. Conversely, what NFL teams can’t coach is improving one's arm strength, or becoming more mobile to make off-script plays outside of the pocket. Those are innate abilities that you either have or you don't.
They are the baseline traits for an elite QB nowadays. Kyle Shanahan realized that for as smart and accurate as Jimmy Garoppolo is, he's not winning them a Super Bowl because he's limited athletically. The same cannot be said for Trey Lance, and Kyle was so desperate to get this new mold of QB that he traded 3 first round picks and 1 third round pick to do so.
Sean McVay realized that for as good of a game manager as Jared Goff could be, he will never have Matthew Stafford's arm and ability to drop dimes under pressure. Sean believed in a different archetype at QB so much that he was willing to trade 2 first round picks, 1 third round pick, and a former #1 overall QB who the Rams initially traded 2 firsts, 2 seconds and 2 thirds to acquire on draft day. The sunken cost did not matter to him, because he understood that Goff will likely never be enough to win the Rams a ring.
Clint Kubiak, OC for the Minnesota Vikings, is the best example for us Texans fans. Out of the playbook of Nick Caserio and the Patriots, the Vikings took a mid round QB in Kellen Mond, in the oft chance that he can successfully supplant Kirk Cousins in the future. Even though Clint had decades of Gary's tutelage drilled into his brain, he would not be held back by the past.
He realized that while Cousins was a good QB who had great moments - he could execute the wide zone/bootleg heavy Shanahan scheme, and even delivered the city a Minneapolis miracle - Cousins doesn't have a Super Bowl winning ceiling. So he drafted a QB who, might have a small percentage of succeeding - like your other mid round QBs: Garoppolo, Brissett and Stidham for example - but if the Vikings hit the lottery on Mond, they'll be getting the $100m jackpot, not some $50 scratch-off-card.