My stand on the extent I reach through concept has always made time spent on building lesser projects seem trivial.
This line of reasoning is holding you back, and you said it yourself in your original post; your ideas are worthless unless you are able to somehow express them to create an actual game. Unless you make the effort to proceed with the next steps of development your concepts will never be more; they will always remain a concept rather than a playable game.
Working in a sandbox to experiment and having a sandbox within your mind may not seem the same to some but it is exactly how I've approached things.
No offence intended, but this just proves that sticking to concepts and thought is inferior to experimentation -- if your approach was equal or superior you would have some results to show, but you're still stuck with nothing more than some ideas in a database and will never go further without taking the next step towards implementation. If you share your ideas you'll have the chance that someone else might make your ideas real, but it's just a chance -- the only way to definitely take your ideas to fruition is to make it happen yourself.
I don't mean this to be discouraging at all, but rather to point out that you can take your ideas to the next stage of development and perhaps even see them through to a completed product if only you're willing to put in the time and effort to do so. Not only that, but with the wealth of information and good quality tools and engines now available cheaply or in some cases even for free it's easier than it's ever been to do so!
In truth, game design is as much science and engineering as it is art, if not more, and you just can't do science without experimentation.
Absolutely, and this is an area talented an successful developers have put a lot of work into, such as Daniel Cook's "Chemistry of Game Design" and other articles, many of Ernest Adams' "Designers Notebook" columns, and a great number of other works. Thinking and dreaming will always give you nothing more than thoughts and dreams unless you're willing to put in the additional work to implement your ideas.
: Elaboration, added some text to be more obviously encouraging.