I'd agree with you that it was a shorter run than the 60s Celtics, 80s Lakers, 90s Bulls, etc., but I still think having a five year run with a 73 win season sandwiched in between two 67 win seasons plus three les is good enough material for a modern day NBA dynasty. It seems this debate got a little off track though-- the original point was that they built the core of their team primarily through the relatively ordinary draft picks of a #7 + a #11 + a #35, and I'd still say that's pretty impressive. Teams like Sacramento, the Knicks, and quite a few others have consistently had similar or better chances and not even produced playoff teams.
Durant's a whole other topic, but I've always sided with him & the Warriors on that one. Staying with Westbrook would've simply been a bad basketball decision on Durant's part, and I think more & more people are seeing that. I can't fault a guy for wanting to play with guys who play the right way fundamentally over anchoring himself to Russ. People were dazzled by Westbrook's number for a while, but most have come around now to the opinion that his style of play-- low efficiency shooting, poor shot selection, laziness on defense, high usage rate, high turnovers-- is not conducive to winning championships. I'd judge Durant more harshly if he'd stayed in OKC for sentimental reasons, ignoring the fact that it wasn't the best move to make at the time.