the only challenge that i can think of which really matters is adoption. and that is not something you can fix, it is something that is fixed on its own with time.
as time goes by more people find out about bitcoin and more of them start using it. some are merchants and some are users and they all make the ecosystem grow.
Adoption covers it all in my opinion, like adoption is both being halted and being promoted throughout the time because of these bans and regulations happening. Adoption, when we put it in a flow chart, is like the highest or the top thing that Bitcoin really needs to get into. It isn't just the innovation of coins, stabilizing the network, forks, and price movement that challenges the Bitcoin as an investment and currency. I agree to the user I quoted.