These coaches would be considered average at best if they coached teams lacking (some) talent like the Rockets. Instead they are the elite of the elite, due to having teams that are loaded with talent. Add Spoelstra to the list as well. Reality is they would all get 10 wins with the Sixers. Coaching truly does not matter that much in the NBA. Hope this makes you feel better with the upcoming hiring of Pringles. Only negative is that he is an ahole as a human being and the players may pull the same crap they pulled on McHale last year.
In 2008, Spoelstra took over a Miami team that won less than 20 games, and in his first season, not only did they make the playoffs, but they were a five seed that took a very good Hawks team (who took Champion Boston Celtics to 7 games the previous year) to 7 games. In his second season (2009-2010), with a worse roster (since Riley was cutting salary to save up for Big 3 free agency in summer 2010), he won 47 games and was the 3rd seed in the East. He earned the right to coach the Big 3. Now, look at what he did this year. He took his team, which was constructed around Wade and Bosh, to the 2nd Round of the playoffs - where they lost in seven games, despite not having Bosh during the entire second half of the season.
Reality is there are only a handful of coaches in the NBA capable of building the team culture thats required to win a championship. Basically guys who the superstars will listen to. Unless you have those coaches, coaching doesn't matter.
Spo is not bad. But Wade played like 50 games in 07-08, Riley was mailing it in and they were tanking for Beasley/rose so they happily won 15 games. Spo took over the next year and Wade was a top 5 player leading them back to the playoffs. I think that was more of Wade being awesome in a weak east than Spo being anything special. I mean seriously. Wade was a beast in 2009 and 2010 before Lebron came. He's not bad but he's not considered along the lines of Pop or Rick Carlisle for a reason
Each of the years you mentioned he had a little known hall of famer in his prime named Wade. Not the big 3, but in the East certainly good enough to get you some success. 90% of the NBA coaches are nothing more than figurehead cheerleaders. Riley, Popovich, and a few others being the exception. Give any coach the big 3 in Cleveland and he will win 50 games minimum. Mike Brown, Byron Scott, and our new friend Mike Dantoni being the rare exceptions of coaches who actually have a negative impact on team performance.
Give me examples of Byron Scott and Mike Brown having negative impacts on team performance. I can only think of Brown being outcoached by SVG in the 2009 ECF, but he won more than 65 games that season and was Coach of the Year.