Great post Ian! I can certainly relate on the lack of marketing experience but, I can't say that I agree 100% with your verdict that the success of a product rests solely on how specific a problem it solves. Depending on your product's niche, you might find yourself struggling with marketing a product because your potential paying customers are used to general purpose apps that solve most of their pain points, even if not all. Just because those general purpose apps, as you've put it, create such little friction.
For example, I'm working on a startup that caters specifically to runners. That's it. We analyze run data and create nifty little visualizations. The upsell is even cooler forms of analysis that someone like a track coach, amateur, or competitive athlete might use. It solves a very specific problem: "how can I tell that I'm improving as a runner?" and it has very specific answers like "you shaved 25 minutes off your 5K time based on your best runs over the last 90 days" or "in the last 30 days, you've spent 65% of your training at a pace faster than 7:30min/mi (your tempo pace) - you're in danger of overtraining or, worse, getting injured!" Although, I can't even begin to tell you how many people have told us to generalize our app. Include cycling, swimming, hiking. Maybe somehow tie it to nutrition or weight loss. Maybe also vie for the role of becoming the Facebook of fitness. And, of course, the number of times that we chose to turn down the temptation to diversify... I'm all for staying focused. Running is the first and last thing I think of each day, but I think it's also safe to say that being specific can sometimes equate to being esoteric and, that, can sometimes be a long and difficult road to follow. I'm not saying it's not worth it. I'm pretty happy. Although, it doesn't grease the wheels for success indefinitely.