Mining isn't (primarily) for currency issuance - it's decentralization of secure transaction processing. Which still isn't something everyone considers important, of course.

Of course bitcoin's major advantage is that it's already here and working.

Certainly. Using it to distribute the currency, before there's the critical mass of people wanting to make transactions enough to pay your miners seems a perfectly good fit once you're already needing to mine, though.

"There are (theoretical) systems that allow cryptographically secure transactions to take place without so much thrashing though. Even verifiable offline transactions."

Verifiable offline transactions with no centralization? Can you link to some?

Nope, because they all have centralisation, as I said, the thrashing is the tradeoff!

And no, not everyone values decentralisation, sorry. I ddon't consider it an important aspect of a currency or payment scheme. Good for you if you do. Personally I value consumer protections and ease of use way more.