If you want api keys to replace passwords then users need a built in mechanism on their device that stores it, since the majority of people are not going to be

If you want api keys to replace passwords then users need a built in mechanism on their device that stores it, since the majority of people are not going to be able to or want to copy some long obscure token and store it somewhere for later access. Some devices already have password managers and similar mechanisms built in, but it needs to be universally implemented and accepted before you could do something like this. Then there's still the question on do you share the api keys across devices?