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.
Who cares if they use laptops or big servers?The broader point is that Bitcoin grants anyone with such a laptop and pipe the (revolutionary) option of being their own (disruptive) financial institution.
That no one can't really use anyway because it is either A. Too costly or B. Transactions get never confirmed. 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." Irrelevant to the question.