> seems most of the interesting cryptocurrency activity (like million dollar liquidations) happens entirely off blockchain, on centralized exchanges (maybe?).
Correct. I commented this before, but if you compare (for Bitcoin) total daily transaction volume from Coinmarketcap (which probably isn't complete) to the actual transaction volume on the blockchain, something like 80% of transactions does not involve the blockchain. At least, that's from the top of my head from the last time I did the math. And those blockchain transactions are probably in part moving from hot to cold storage by exchanges and people moving around crypto through personal accounts.
If decentralization is the main feature of crypto, then we might as well stop using it right away, since nobody seems to actually care about it.