I work at a US Government agency that deals with Crypto-crime. Yeah, we're as busy as you might suspect.

Blockchain is a distributed database. That's it. That's ALL it is. Distributed databases have been around for decades.

Now, the problem with crypto's particular implementation of a distributed db (aside from the energy requirements even with PoS systems) is that it handles concurrency LIKE. TOTAL. SHIT.

A real distributed financial DB, say for an institution with locations in LA and NY, has entire clusters of extremely beefy servers in both locations and a fiber line dedicated just and only to it (multiple, actually). The servers are clocked to within millionths of a second or better, and take into account things like elevation and the mass underneath (basically, just like GPS satellites take those things into account), so that they go out of sync by one second per longer than the human race has been or will be around.

They do this so that if two transactions hit the same account on opposite sides of the country, there's very little chance of a timing collision.

Now, take that database, put it on a typical virus-infested home PC, where it's perfectly happy being five entire minutes out of sync with everything else, the owner loves playing LoL or Dota2, leaving precious few cycles available for anything else and do the following:

1. Figure out what time a transaction was actually posted, and
2. Actually, just load a few hundred million heavily encrypted transactions and try not to turn that PC into a smoking hole in the linoleum.

It'll "work" as long as volume is low. As volume goes up, computing requirements go WAY UP, concurrency becomes a huge problem - we're not talking about your personal bank account anymore, but something on the order of Capital One's accounts, with thousands of transactions per second. You want Crypto to replace Wall St.? With a bunch of SETI@home PCs?

BWAHAHAHAH, no. It can't handle that sort of volume without imploding LONG before you approach even a meaningful percentage of what the Street handles.