"This is nothing new", "I could build this myself", "you have to install something, nobody does that", etc. etc.
The key to a successful company is not being first, not (only) having a great technical solution, and not having tech noone else does.
The key is an umbrella of technology, business sense, marketing ability, salesmanship and much more. Andreeses/Horowwitz probably see a whole umbrella, and not only the tech.