In a nutshell you are saying decentralized advocates forget about the bell curve of "effort" humans are willing to spend.
Isn't this just a design problem, as opposed to an intrinsic problem with decentralization?
I believe that we can design convenient decentralized systems. We definitely have not done this yet, but that does not mean this is an unachievable goal.
There are also human factors which currently are a problem too. The massive increase in people using internet technology (via smartphones obv.) Was not accompanied by massive increase in technology education/expertise.
The early users of the internet were extremely technically capable in comparison, raised on microcomputers. Getting online was a hassle, but presented a fun challenge to these people.
Not only are today's platforms essentially closed, the average user has a lot of difficulty understanding all the layers required to do something like say, set up an email server. This is a major drain of effort and it's just one piece of the networked tech people take for granted.
However if there were simple alternatives which could be setup and used "effortlessly" people would use them.
Web3 is an unfulfilled promise, so far, and is in a phase where scams and bullshit are rife.
It's unlikely that people will perpetually be satisfied with the centralized services, especially as they continue to degrade in service and ethical quality. A process which may be part of the equation which leads to better decentralized systems which are also secure and simple to deploy & use.
I think the interest is there, the technology isn't yet of course.