Photographers care most about their images/galleries. Restaurants need menus. Real estate agents need listings. All of them need different types of forms.
The trap with going general first is you'll either have to (a) build a "kitchen sink" product with features for everyone or (b) have a product that many industries don't want to use because it doesn't have NICHE FEATURE X.
When you go industry first, it's easier to get traction and recommendations. It's easier and cheaper to advertise to your audience. You can guerrilla market yourself at trade shows and find "industry rockstars" to champion you. You can totally dominate that industry and have a nice "lifestyle business" or simply use it as the first pin in a bowling pin strategy [1]. For example, we're pretty deep into the photography space and now we're taking one product and going after Architects.
Obviously Weebly and Squarespace have had success being general-purpose. So, now you're basically competing with them + wordpress with your main advantage being "mobile first and responsive". You say your format is suitable for small-businesses. I'm sorry, but in my experience that's not enough to get people to switch.
We've designed/sold/deployed/hosted websites for a few thousand wedding/portrait photographers plus almost the same amount of high-end commercial photographers. Don't take this the wrong way (your designs are beautiful) but I can't see any of my clients jumping ship to a product like this. (FWIW, most clients we lose go to WordPress or just go out of business).