OTP verification can largely be worked around because so many sites still use SMS codes which a dumb phone can handle. Similarly, 2FA codes can be handled on a PC without requiring a smart phone. It adds hurdles but can be done.
Where it becomes challenging is situations where smart phones truly are required. When I attended college football games last fall, all tickets were e-tickets. You were required to present a QR code on your device or your ticket stored in Apple Wallet or Google Wallet. I ran into the same situation with my local theater's ticketing. You haven't lived until you've witnessed an audience with an average age of 70 try to figure out their tickets on their smartphones when they've never used them for that before nor had any notion that was even POSSIBLE.
Where it becomes challenging is situations where smart phones truly are required. When I attended college football games last fall, all tickets were e-tickets. You were required to present a QR code on your device or your ticket stored in Apple Wallet or Google Wallet. I ran into the same situation with my local theater's ticketing. You haven't lived until you've witnessed an audience with an average age of 70 try to figure out their tickets on their smartphones when they've never used them for that before nor had any notion that was even POSSIBLE.