I know a few of the true stories behind the original logos of some of SV's unicorns and this is spot on (unfortunately, I cannot share them because they were shared in confidence). The parent comment is not wrong about the value of a great brand, but it can easily become a huge frivolous distraction after a certain point when you're should be focusing on building something useful for people in their daily lives. You can always perform a full brand refresh later once you can afford to spend a few months and lots of money to do so, and that's exactly what many unicorns eventually do.
I've seen outside designers rationalize some of these well known brands after the fact without knowing the inside and often accidental story and its comical. It's brand design. Like all the other components of a great company and great product, it's contributory like engineering and customer service, but it's not like you're solving World peace. For some products/services and target markets, the brand may be very important. For others, it could be non-consequential. "Worse is better" and "perfect is the enemy of done" apply to brand design as much as in any other aspect. Like other aspects you can always iterate and improve later.
Your pitch is important, and tone of your copy is important in framing and expressing this. For example, if you're asking me to download an executable you need to gain a certain degree of trust on behalf of the user. Trust is an emotion. Good art & copy can go a long way to building trust.
Branding is really the emotional connection you make with your user base, and emotional connections aren't rational things. This is why excellent products sometimes lose to less functionally valuable products - because we've distilled the rational meaning down to something which is irrational.
To "like" Apples products, for example, is not rational - it's emotional. The meaning behind Apples brand is more than the functional value of it's products. It represents something different to each of us, even though we're all using the same product. For some people, Apples brand represents a part of their own identity - this is about as emotional as it gets. Apples brand communication has touched these people in a strong way. Do you think Apple could have built such a loyal following with a MS Paint logo and terrible copy?
To put it another way, branding could also be thought of as packaging - and it's well known that packaging is extremely important to product success.
Spending tons of money on brand design, when you really need a minimum viable product to get you going is not a good plan.
Once you've worked out you have something of value, that people are willing to part with their cash for, then by all means spend tons of money on it.
That's not to say there's no value in well made branding, but it's just not something that an early startup should care about much.
So when this site came up a long time ago in /new, I grabbed one of it and put it on - only because my product contains a Chrome Extension, and it needs a small 32x32 icon. And, it is a damn good logo too. I also sent an email asking permission to use it, and even offering to pay (peanuts) for exclusive access, and the founder was extremely courteous and reminded me that it doesn't matter what you start with, you can always change once you get traction.
So there you go. I love my generic logo.