Based on my own direct experience and those shared by others in this and similar forums, I think the biggest challenge to implementing GTD is that it flies in the face of the traditional "time management" principles most of us are taught. In a lot of cases it is our preconceived notions that get in the way of adopting GTD rather than any inherent flaws in the methodology. It sounds like that's what you're facing.
The difficulty in challenging in our assumptions is that we often don't recognize them or even give them any thought. I used to weigh 300 pounds and I couldn't run an eighth of a mile if a bear was chasing me. For the longest time I accepted that this would be my lot in life, something beyond my ability to change. Today I'm at 215 lbs and last Sunday I ran eight miles in preparation for a half marathon later this year. The hardest part of achieving this wasn't the work involved, it was changing the underlying assumptions I held that prevented me from doing the work. I think GTD is similar. It's hard work, but the hardest part is changing the assumptions that get in the way of doing the work.
I doubt that the "crowdsourced" solution you're hoping for will help you very much. While you're certainly not alone in experiencing the challenges you've described, there is no universal solution for them. You have to find what's right for you.
I think
@Longstreet offers very sound advice. I'll add a couple things. First, if engaging a GTD coach or joining GTD Connect is outside of your budget (as they are for me) and you can't find or aren't interested in a GTD buddy, just participating in these forums can help. In the last two months forum members have helped me clear away two big roadblocks with my GTD practice.
Second, there is no software that can make GTD easy or make your practice successful. Moreover, you don't need any particular software feature to be successful. You can successfully practice GTD on paper if you want to. I use software called Evernote that isn't designed for GTD and isn't even a traditional list manager but it works very well for me. I'm not trying to sell you on Evernote, but to help you challenge the assumption that "GTD requires a specific kind of software." The only things GTD really requires are an open mind and diligence, and those are things that come from within.
Finally, I agree that GTD requires an investment of time. But there is a cost to managing things in your head that often goes unaccounted for by most people because they don't think there's another way to do things. I started trying to practice GTD in 2007 but only really got serious about it three years ago. Every time I wonder whether GTD is worth it I remember how inefficient it was to have to repeatedly sift through emails in my inbox trying to remember what's actionable and what's not, or the time I would spend dealing with stuff that had blown up that would've been quicker to deal with at the time it had shown up, or dealing with crises arising because something had unnecessarily fallen through the cracks.