"What stops my physically moving the RFID to another frame?"
Nothing. That's only there to make data entry easier and less error-prone. Maybe you could build one that it tamper evident. This portion is really an aside, a value-add.
"If you have tamper evident seals - why do you need a ledger?"
So that you have visibility into the paper trail easily and quickly, anywhere you have Internet access. A sealed container doesn't on it's own tell me where it came from or what's in it, or what stops it made along the way.
"Could the problems be solved with a normal database based on PKI?"
Sure. But those systems have failed to generate buy in. Blockchain has created that. Is it because people don't really understand it? Maybe. Is it because it's genuinely unique and better suited? Maybe. In the end though, neither of those details really matter. We've been trying to go paperless and distributed for decades, and none of the other advancements we've made have made significant progress on those end-to-end. Blockchain looks like it will.
"If pirates can take over 50% of your chain, can they hide their smuggling?"
If you use a permissioned chain, rather than a public chain, not likely. At least, no more likely than any other Internet-connected system getting taken over by bad actors.
"Blockchain is amazing technology - but it is a solution in search of a problem."
I used to think that too. Seriously, go watch some of the talks I posted above. It's likely your opinion will shift a bit.