Decisions about what? The low-hanging-fruit software companies have already been built; the most successful new software companies are all about a specific vertical, and this requires specialization.
Trivially, yes it would be best to be 100% expert in programming, 100% expert in marketing, 100% expert in business, and 100% expert in whatever the business domain is, but that isn't feasible. That's why most new start ups have a founding team, not a founding superperson.
I'm not buying it. What companies are you thinking of? I feel like I will either find them seeking out a generalist for some subset of their workload or a company that is just as young and valuable that hires massive numbers of generalists (e.g. Uber, Postmates/Doordash, WeWork)
Trivially, yes it would be best to be 100% expert in programming, 100% expert in marketing, 100% expert in business, and 100% expert in whatever the business domain is, but that isn't feasible. That's why most new start ups have a founding team, not a founding superperson.