If the block size remains at 1 MB, most of humanity will be forced by necessity to transact off chain.

The rationing is a form of artificially subsidizing off-chain solutions, causing them to see usage that they otherwise would not if people were free to choose between on-chain and off-chain transactions.

OT has many other uses besides financial transactions so it would be fine even if Bitcoin handled all the world's monetary transactions. If Bitcoin is not allowed to step up to the plate, however, OT (and other off-chain systems) would need to take up the slack.

That's not a particular great scenario. It'd hardly be better than the fragmented and high-friction financial system we have now.