Your problem is you pre judged Doc based on what the fanboy in you wanted to see. When he lost without talent it was because he was a lousy HC. When he won with talent it was because talent is all that matters. When they lost a couple of games mid season you were right back to coaching matters irrespective of talent and Doc is a lousy HC. Then you determined they could not win with him in spite of talent. You were dead wrong, in part because you never understood what was going on. They were building something here. All you wanted was to win every game. You do the same thing with McDaniels. Danny and Doc, like Bill, understand it's all a process.
Doc developed those players and unlike his predecessor he was willing to take his lumps and losses in playing or disciplining them as they developed. That dramatically increased their post draft value potentially at his expense. Then he took a kid like Perkins who most saw having little potential as anything more than a backup center and developed him into a starting center with a crucial role on a defensive minded championship team. He did the same with Rondo. He did that by both playing them and disciplining their play. He made them earn their minutes including in practice, just like Bill does.
What makes you think the coaching staff is independent of Doc other than you want it to be? Danny is a hands off GM who acquires talent and stays out of it's way - and that includes the HC provided he is willing to risk his career standing to embrace a mutual long range goal. Doc hired Thibideau, Danny had nothing to do with that. Doc had feelers out to lots of coaching help including Larry Brown, a bright guy alternately known for stabbing folks in the back. He could contemplate that because he had the courage of his convictions and the single minded goal of making this team better. He knew it was time to transition from coaching a rebuild to coaching a contender. That is why Danny's support for him never waivered even as the nitwit fanboys screamed for his head for two years.
This isn't baseball where players routinely come up through the minors. And still, even there they require a manager with insight and conviction to allow them to make the transition. The talent Ainge acquired for Doc had to learn on the job, either to play in the NBA or play with each other in a system. Few NBA coaches will accommodate that scenario for long because they care more about public perception and future employability and succomb to the need to win essentially meaningless games at the expense of building a strong foundation. Doc was willing to take the abuse and do what Ainge needed him to do in order to develop sound talent either to play now or be used as valuable trading chips to acquire veteran pieces who could win in the forseeable future. What Doc did allowed Danny to do what he did.
Even with keeping Pierce here to win his ring. They butted heads at first, but Doc took some sage advice and worked at winning that player over because in doing so you create your most loyal ally for the long haul. And that went a long way in insuring a Big Three could work here. If the incumbant captain and leader was willing to sacrifice his game for the greater good, how could the other two not follow suit. If he was willing to embrace raw kids and aging role players as equally valuable assets, then those players could envision themselves as such even in the presence of a Big Three. He even found a rallying cry to keep them focused on a collective goal than encompassed all they were being asked to embrace...Ubuntu.
Your problem is you can't begin to admit you were dead wrong across the board where Doc was concerned. He was hired to do more than script x's and o's. Doc's job was to teach and instill a work ethic and committment to team defense unselfish play into this team, to get them back to the kind of teams Ainge won with. To shift the focus off big scoring and big egos onto stopping big scoring by other teams big egos. That allowed Ainge to focus his drafts on smaller, faster players who were more plentiful and less expensive than the big bodies and allow them to survive absent luck of the draw lottery picks. That meant for the most part they won low scoring hard fought games. But low and behold it also allowed them to engineer 20+ point comebacks (via stops) when they needed them most against a more talented but less diciplined foe and a 39 point blowout of the highest scoring team in the NBA to clinch a title. Danny and Doc were on the same page all along - defense and discipline on both ends of the court wins championships. Page out of Belichick's book. Players don't always execute their coaches vision consistently, but when they do so when it matters most they win.