SVG is fine as a coach. It was the dual role that killed him in Detroit. I mean seriously, look at how awful Detroit is within 2 years (with basically the same core) and with the reigning Coach of the Year that followed SVG. He got a bum rap in Miami. I mean they won 59 games and took the defending champs to game 7 in ECF, and then 20 games into the next season Riley fired him so he could get all the credit and after there was mass roster turnover (basically only Wade, Shaq, and Haslem came back). He went to Orlando and took over a 40 win team had them winning 50+ games for 4 straight seasons (now they did add Lewis his 1st season which helped) and took a fairly weak team to the Finals (DHoward is pretty flawed as #1 players go and Lewis isn't exactly a solid #2). He had his spat with Howard who essentially got him fired before everyone realized Howard was just a nut case. Goes to a Detroit team that hadn't won more than 30 games in 5 seasons, and within 2 years has them winning 44 and making the playoffs.
SVG the coach is fine. It was his GM stint in Detroit that was atrocious. No one can really do both jobs simultaneously, but especially not someone that has no experience in the front office. It is just too hard.