Under these conditions the real invisible unicorns are the ones that simply fail to climb out of this hole: they are the billion-dollar companies that are totally unfundable and simply do not make it past that stage and die.
Here is a Quora link to one of the best ideas I've ever heard in my life and easily the basis for building a $50B+ company. I ran across it as a VC quoted it as something like the "dumbest pitch they ever heard."
https://www.quora.com/What-are-the-best-horror-stories-about...
Actually the exact words were: "the most breathtakingly clueless company I have ever had pitch me (and I am not making this up.)"
This company was seeking $2 million only and clearly outlined a very specific growth plan. It is very easy to see the author's reasoning and the clear path they had for $50B+ as well as the likely reactions of other market participants.
If you are a founder of an invisible unicorn, it is important for you to not subject yourself to this ridicule. Not only will VC's waste your time and drive your company into the ground: they will gloat about it on Quora. The correct approach is to completely ignore them and be and stay invisible.
The seed-stage funding climate is completely broken and lots of great companies and ideas die for this reason; a few manage not to die somehow, as we hear about here.
For every invisible unicorn, there are a lot of premature unicorn deaths.
(Actually for this reason the word "incubator" is an excellent one, as it really is like an incubator of a premature birth of a youngling that will die if exposed to the elements and without intensive care and treatment.)