Well put - exactly the same reasons for me.
I have dipped into the GTA games a couple of times and each one lost interest after a few hours.
The shooting is subpar compared to a dedicated shooter. The driving is subpar compared to a dedicated driving game. So a lot of the time you are playing a sub par game. Running civilians over gets old after the first 30 times. Being able to play golf is great if want to play golf, I'd rather get on with the story. Driving from A to B in under 2 minutes is tedious. And crime is just boring compared to sci fi and fantasy settings, not to mention its close enough to the real low life scum to make it pretty depressing.
Great atmosphere and world, but what you end up doing in it is just a bunch of minigames.
So, yes you are not the only one, I'm one of the other 6 people not playing it.