Someone gains access to your private key and you just… don’t own your house anymore?

Depends on a) what keys you have, b) who even gets to make mutations and c) if the system has provisions for "edit" transactions (which don't change history but say – to put it very simplistically – that eg. "previous transaction x is invalid"). Also it's unclear why you think this is different from a database password being stolen.

Your point about how building a secure, central database will have so many technical hurdles to overcome is… odd. I mean, sure it’s tough to make a secure database. Your answer is that some blockchain framework has certain security characteristics while ignoring that literally every secure data store that currently exists is running on a central database and just fine at that. Like, what do you think that your bank is using at this very moment? There are multiple companies with well-audited solutions selling and running secure databases RIGHT NOW. You just hand wave away the ability to make secure databases while ignoring that they already exist while expecting us to buy into the promises of some new, unproven framework like Hyperledger. The only thing that blockchain adds is immutability, which is something that I think would be a poor idea anyway.

I wasn't saying to throw away existing systems or that banks aren't running secure databases. Jesus christ you seem more intent in just being indignant about me daring to have a differing view about something than actually reading what I said.

You also clearly don't understand what Proof of Authority means and didn't bother to read my explanation, since PoW / PoS are completely different consensus mechanisms and the problems with them don't apply to PoA systems.

This is a false comparison. You do not have to build these features yourself. Like, have you heard of this tiny company called “Oracle”? Or maybe this really obscure one “Microsoft”? They both make exactly this product.

Remind me which Oracle or Microsoft database solution gives you signed state mutations, a guaranteed immutable and tamper proof history out of the box.

Honestly your whole argument relies on you not bothering to read what I wrote and then answering with sarcastic comments based on what you assumed was said. I know you don't agree with me, but try not to act like a twat just because you don't.