I think the first factor to increase adoption, of anything anywhere, is make it mainstream. I’ve ever hated MSN, facebook and orkut, and was forced to join them because too many ppl were on them.
For cryptocurrency, its wallet needs to be very user friendly, must feel secure without requiring advanced knowledge, must protect users from hacks and scams.
That solved, we have the scalability issue. At least in Brasil, we have a handful of companies offering credit cards totally free of fees. Cryptocurrency won’t succeed if we have to pay fee for every transaction we do. I know it’s healthy for attracting nodes, but it scares users. And some networks are too slow which makes their fees expensive. Cardano is working nicely to make its blockchain scalable.
Then we have volatility issue. No company is willing to accept payments on a currency whose value change a lot. They receive a payment today and tomorrow it values 20% less and their profit is gone. Many companies had accepted BTC in the past, but used a middleman that would instantly convert BTC to USD and charged expensive fees. That makes adoption even harder and more expensive. The solution I see is inclusion of algorithmic stablecoins, as USDN and DAI. This way, ppl and companies can just use stablecoin instead of the main currency, to flee from volatility.
I also believe that stacking the main currency is the wrong path. That reduces market availability and increases its value, which scares ppl from joining when they see the currency is overvalued. That’s solved by the creation if a currency specific for stacking, node payment, governance, etc. Ppl willing to stack just buy that currency, and leave the main one free to be traded.
Then, for poor companies like we on South America and Africa, I think we must find cheaper wallet solution. Ppl who are really outside banking system don’t have PC or smart phones to be able to use a software wallet. Maybe there should be some sort chip card like credit cards, or even a paper, which stores would use to make transactions. I know these ideas are troubling, I just think we needed some sort of cheaper solution for ppl who don’t own a hardware to manage their wallet.
Education is great, but I don’t see it being able to increase adoption. Nobody will join a cryptocurrency just because they know how it works, if nobody else is using it and they have nowhere to use it for payment.
Poor ppl don’t have money to keep stacked, they just receive their salary and go spend it. In Brasil it’s still very common to withdraw whole salary on the first day and spend it all on the same week. 
We need to take their use cases and needs in consideration to help them adopt Cardano.