There's nothing in GTD that says you can't review all of your context lists first thing in the morning to determine if there's a particular context you need to make available to yourself during the day.
I call this sort of thing "analysis paralysis." These problems you posit are easily solved. I don't think most people have trouble deciding whether to go to work, buy groceries, do gardening, or go to a funeral -- unless they analyze it to the extent you are here. If the unexamined life is problematic, I'd say the overly examined life is as well.
If you are "time-starved" and unable to find time for gardening, and gardening is really important to you, GTD makes it easy to determine what's out-of-whack. If your boss is overloading you with work such that you can't pursue personal interests, the best way for that to become readily apparent is for you to see all of your commitments objectively collected in an easily reviewable format.
As I am getting on my feet with GTD, that's the first thing I've noticed. I am a salesperson and my job often requires a lot more than 40 hrs per week. I am president of the board of a small arts non-profit. My girlfriend and I own a house together, we have four pets (two of whom have health issues), I have hobbies including drawing and writing, I have friends and family to whom I want to devote time, a close family member with a serious illness, my own health to manage...
Do I get to join your "time-starved" club?
Seriously, GTD has helped me in this regard rather than the opposite. As I've been getting on my feet with GTD I've been finding that GTD has revealed where I am over-committed and I can see in concrete terms the tough choices I need to make.