The opportunities for technical disruption are clearly there.
But no sector outside Business Process Software like SAS and Oracle has so much built-up institutional knowledge of how to run direct sales and marketing to enterprise customers as security. The crappiest me-too products are weaponized for enterprise sales 6 months before they're launched.
It's hard to break through the noise.
Your points re: difficulty of enterprise sales are hard-learned, I assume. My intuition says there's an opportunity to exploit there, given the disconnect between users and industry. Of course, the same is true of cell providers, but no one has managed that one yet either.
There are early adopters and there are influencers. But in enterprise sales, they're rarely the same people.
Among 2000 billion dollar enterprises, there are perhaps 20-30 with strong security teams with the bandwidth to truly engage with new technology (as opposed to simply running a bakeoff and deploying a product in a category that a trade press magazine says is important). Those are influencer early adopters.
Open source allows you to release something early and maybe catch the attention of those influencer early adopters. A scrappy sales team that can take a meeting with a new customer and put a couple F-500 deployments on the logo slide because they've got Github followers has a shot at getting pilot deployments.
Open source is also "free", in the sense that enterprises can't not spend money on software; deployment decisions follow purchasing decisions, not the other way around, so the drumbeat of technology at an enterprise is purchase orders. Try hard to give your software away at an enterprise; nothing will happen until you give them a way to pay you money.