Dan invented the concept of "blockchain company". In these kinds of companies in my opinion the CTO is most important at least during the early stages. CEOs build partnerships but you need a fully functioning technology first.
Even if what you say is true I'm not seeing a lot of success on the building partnerships front. Who has Steemit partnered with? I see no partnerships with ad companies or other social media companies or with universities. I have seen some people try to use Steemit API and develop on top of it but the fact that Steemit isn't open source could be a problem.
It is what it is, but for the most part I think Dan was important because he wasn't just a developer but he was principled. Lately Steemit seems to have been focused on making a quick buck with no long term vision and I saw it happen when they first changed from 2 years in the contract to accelerate the power down.
I don't think there is any CTO who will be better than Dan Larimer, who will know the code base better, who will be as trusted, or who has the right principles. He was irreplaceable for this particular vision and without him then if he leaves a lot of people will follow him who share his vision.
Steemit will survive, just like Ethereum could survive without VItalik, but it's a major loss.
Exactly as you say.