a major barrier to adoption has been the community's reluctance to embrace "off chain" payment systems.
It depends on what you mean by "off-chain". If it means using a third party like handing over your BTC to VISA and then they let you use your money (or not let you use it some day) then it is not just reluctance it is about the fact that using third party defeats the whole purpose of bitcoin! Not to mention that loss of security and privacy.
But if you mean a second layer that sometimes referred to as "off-chain" such as Lightning Network, then it is being used and it needs more time to grow in adoption. Again there is no reluctance here, just needing time.
Bitcoin's network is simply too slow and expensive for the majority of day to day transactions.
It is neither slow nor expensive. It is actually funny that you mentioned VISA since VISA is more expensive and extremely slow compared to bitcoin.
Both bitcoin transaction and VISA transactions are validated in seconds but bitcoin transactions take on average 10 minutes to be settled while VISA transactions take months to be settled.
Now what if Visa added BTC as a supported currency? That would be big for adoption. Consumers could pay their bills directly in BTC. Merchants could receive BTC from Visa.
Why use bitcoin then? Just use VISA and their IOUs backed by USD.
Basically, all criticism about the Bitcoin payment network would become moot.
Wrong. Using bitcoin itself becomes moot. The point of using bitcoin is that you no longer need a third party and remain in 100% control of your own money. If you give that up that means you didn't even care about the idea of bitcoin in first place!