2. Now, what's a valid use-case for a smart contract, and please explain how it functions if there's a bug in the contract?

3. Maybe. You'll need to provide a more concrete use-case. Also, you have the outside-world problem (you know the data hasn't been altered, but you don't necessarily know where it comes from).

4. All you need for decentralized identities is a public key. (Though if you want your identity to be long-lived, you'll have to also have a system of secure key rotation, and the most straightforward system is blockchain-ish in that it involves a signed append-only log. But it doesn't need a global trustless ledger.

5. See 1, except worse, because the transaction cost dwarf the actual payment.

>5. Microtransactions for online games and to replace web advertising

how money transfer and microtransactions are different?

So. No applications it excels at.

> To dismiss the entire technology because of (admittedly a lot of) grifters is premature in my opinion.

It's been 13 years. When will dismissing it become mature? In another 13 years?

Or maybe the tech is just bad.