I think there are a few factors that can increase mass adoption to a certain limit.
- Price factor; ultimately we are all in it for the money incentive. Higher price drives higher interests, efforts, and involvement.
- Institutional factor; if the retail level cannot take lead, then the adoption will need to be driven by institutional participation.
In term of UX, how simple can it really get? Ultimately, the users need to be aware that they have a significant responsibility to secure their private keys safely. (Are they going to let their smart phone do it for them? Of course, but make sure they never lose their smart phone. Is the protocol going to change whereby private key is no longer necessary? Sure, I always believe having a central authority can sometimes still be the best solution.)
But if having such control and responsibility is a massively tall order, then giving such control and responsibility away to a 3rd-party (which is no longer trustless) to manage the private keys, then that really defeats the main purposes of having blockchain in the first place.
Having mass adoption is probably never going to happen. At best there will be mass adoption among those whose occupation is very closely related to blockchain technology or stand to benefit greatly from it and those whose occupation is unrelated but they are personally motivated enough to get involved.
We cannot expect everyone to be in the world of cryptocurrency and blockchain just as we cannot expect everyone to be in the stock market and futures market. There probably will remain a significant segment of the world population that will just not bother because they are not tech-savvy, or because their occupation does not require such involvement, or because they just don’t care.
Do not waste time on such segments of the population. Instead strive to improve on the needs of the segments of population that choose to get involved and choose to care.
Just my opinion.