Steemit is mathematically designed to collapse in on itself (yes, I've read the whitepaper).
The white paper is out of date. The business (economic) model has been changed.
As for the rest of what you said, I'd only ask why that same logic hasn't caused the demise of every social media ever developed, and, if not, why not? (Then you'd probably be on to why Steemit just might not only survive, but also thrive.)
And likewise every other coin, especially those that distribute new tokens, which is most of them.
BTW, if you look at 'dottom's post history you will see clear signs that the account was recently purchased. It was completely idle for 3 years and has only posted FUD about steem/it after reawakening.
I don't know who is behind this paid FUD effort but candidates include a speculator who has a short position (OTC short, since there is no exchange shorting afaik), an investor who wants a cheaper buy price, or someone supporting one of the competing projects (not sure which one, as they all seem a bit comatose). As always, apply some logic and follow the money here. What logic is there behind someone who has been around crypto since 2012, but not commented at all since 2014, to all the sudden break his silence to start warning repeatedly about the crash of the #18 coin? Does not add up.