Just got some Diafine for Christmas.

Okay, so I go to read the instructions. It's one sheet of paper, single side, barely bigger than a post card.
I have a hard time believing it's really THAT simple.

Whatever film you've got... Just put it in there. Three minutes... five minutes... whatever? 20 C... 25C... more or less?
Okay, I'm being a wise guy, here, but REALLY?

I've been spending all this time fussing around with times, temperatures, dilutions and all that junk when I could have been using Diafine all these years?
Is tweaking your film is as simple as changing your in-camera exposure? I usually do that anyway.

Am I missing something, here?

Why isn't everybody using Diafine?