Something that often gets said, and in many fields other than game design, is the "put up or shut up" argument. Basically, this argument claims that production/performance is hard work, whereas "ideas are cheap", and then makes the further claim that your ideas and criticisms are worthless until you've experienced the trials of production and prove that you can produce/perform them into concrete objects/experiences.
There are three reasons this argument doesn't hold water.
#1: Ideas and production are separate, though related, skills which are often found in separate individuals.
Extremely few persons are masters of both detailing ideas and realizing ideas in concrete productions. Most people are much stronger in one endeavor than the other.
Many successful business relationships have been formed between individuals who represent the opposite extremes. A classic example is songwriters and performing musicians. If Beethoven never learned to play an instrument, who would care? Nobody. He'd still be revered as a great composer. I know exactly what it's like to be able to create music I can't perform, and I admire plenty of excellent performers who can't create. Architects and construction managers are another good example (a buddy of mine has been both).
Learning one helps with the other, but don't discount the folks who specialize in one end of the spectrum. Expecting all people to be proficient in both creation and production is just plain silly. Keep an eye out for the programmers and artists with technical mastery and no imagination; listen to the spacey dreamers who will never finish a project of their own.
#2: Ideas aren't always cheap, and production isn't always expensive or hard work.
There is such a thing as inspiration (Eastern thinkers might prefer wu-wei). Sometimes, ideas flow effortlessly. But deep and careful planning often requires a significant investment of time (which, as the saying goes, is money) and exhausting effort. Even if we're only talking about design theory, is anyone really going to claim that Aristotle's Poetics, the philosophical treatise on aesthetics still used as a literary guide millenia after its conception, was cheap or easy? And note that Aristotle never wrote a play, himself.
That it's an extreme example doesn't detract from the point I'm making: ideas can be expensive. Not every "armchair designer" is speaking off-the-cuff. Careful, deliberate thinking can be arduous. Most people know what it's like to give up trying to reason something out because it's too difficult and exhausting. Theorists and dreamers don't have it easy.
The flipside of that coin is that flow occurs just as often in implementation as with ideas. It's not only possible but common for implementation of ideas to flow. My main point, however, is that we should acknowledge and respect the hard work of both creators and implementors.
#3: The ignorant are full of wisdom.
Parents are often amazed by the deep wisdom that can come from young, uneducated children. Likewise, even idiots and hopeless idealists occasionally offer profound insights.
I have yet to meet anyone who didn't have something to teach me. If you're willing to talk about deep, specialized subjects with kids and adults with very little knowledge on the subject, you'll be surprised how often they say something or do something that really gets you thinking more deeply or broadly. The large and fragmented societies of our modern age have developed an obsession with experts; to highlight some simple clarity in the constant noise. There's much brilliance and beauty to be found inside the noise... if you're willing to be patient and tolerant; to keep looking and listening (to even the ones who annoy you).
I was gifted with a unique chance to learn that lesson, being autistic (which means I've always prioritized logic and truth over culture and social ease). I assure you: if you listen only to the experts, you're missing out.
...but they do have a point.
"Put up or shut up" isn't without an element of truth, of course. People often use the expression after they've heard a particular criticism for the hundredth time, in which case the words might not be any more meaningful than "damn!" (in other words, it's an expression of emotion, rather than logic). But the truth is that experience does matter, and confidence in ideas is sometimes due to ignorance. That realization, though, should be balanced with the realization that experience is not always necessary, and untried confidence is sometime soundly and rightly based.