Hi Adam, welcome to the CHT community! Nice to have you here 
I agree that from a technological perspective the web is decentralized (in its core technologies). The centralization takes place in the ‘higher layers’, as you rightfully say. But I am thinking of the web as the concept that an everyday user of the internet experience, and the vision of Tim Berners-Lee wrt the web as a medium of freedom. So this expression accurately describes it, I think:
" A Decentralized Web is a network of resources in which no one player can control the conversation or spin it to [his or her] exclusive advantage. "
Simon St. Laurent, O’Reilly Media
And this is less and less the case with big tech monopolies and walled gardens, etc.
I am very skeptical of blockchain at the moment, though it could still grow into something useful. I have posted about my perspective, here and here.
Do you mean with ‘commune ways of living’ that decentralization creates a fragmentation into separate small(er) communities? I think this may be the case, but not necessarily a bad thing, especially when having them interlinked in a ‘web of co-op’ and based on open standards. Also don’t know if that would necessarily hamper investment.
Maybe change investment models… interesting subject, maybe create a separate topic around it. We already have Who will invest in humane tech? , Business model innovation and Are humane-tech apps non-starters?