I definitely view it as a negative / risk factor, but I have and will again.
What I really look for is if there is someone besides the CEO to truly carry the load. The load of making it happen — whatever it takes.
A great co-founder is one way, and the most common way, to get help here.
But it can also be a VP you hire after the fact. You can hire “ex-post facto” co-founders, or something close to it.
When I see 2, I get more comfortable. 2 carrying the load. I’m less dogmatic on the title, and the time of joining, of the second one.