Honestly it takes to much team work. Players today are coached to be one on one scorers, athletic post players, (or in my case) the short PG who creates off picks and shoots threes. Coachs no longer take the time with young players to teach the rotation and floor spaceing, which are the most important parts of the triangle offense.
Then there's the issue that few big me set quality picks anymore. The triangle offense creates nothing with the pick option if a big doesn't set it correctly (because no space is made between the guard and his defender).
The 'pinch post' option requires a PF who can pass, and PF's are groomed as scorers nowadays.
The center, who is the back to the basket post scorer commonly in tirangle offense, no longer exsist. They are PF who face up and call themselves centers, or defensive experts.
The triangle offense was not created for the modern NBA, at least to me. That's why Phil uses a much different version for this current Laker team.