Again: The true value that Bitcoin brings to the table is not "everyone gets to write into the holy ledger", it is instead "everyone gets to benefit from sane and non-inflationary financial instutions whose sanity and honesty are ensured by the holy blockchain".
Basically you can't reply to the simple question of "who is going to run a node for these financial institutions?". Gotcha.
And you keep talking about keeping the blockchain decentralized? What a joke you are.
Financial institutions may run their own nodes, hire a specialist, or use SPV. The point, for the sake of the network remaining diverse/diffuse/defensible/resilient, is to maintain the option of "really" (IE trustlessly) using Bitcoin for anyone with a $300 laptop and 1Mb upstream.
The broader point is that Bitcoin grants anyone with such a laptop and pipe the (revolutionary) option of being their own (disruptive) financial institution.
Absent a crackdown or other type of crisis, most people will simply "benefit from sane and non-inflationary financial instutions whose sanity and honesty are ensured by the holy blockchain."
But if there were a crackdown or other crisis, we must ensure that ~everyone is economically and technologically able to "write into the holy ledger."