I agree with UX, but scalability has a working solution in the Lightning Network. However, that needs major UX development...
Bitcoin also needs fungibility:
"Fungibility is the only property of sound money that is missing from Bitcoin & Litecoin. Now that the scaling debate is behind us, the next battleground will be on fungibility and privacy. I am now focused on making Litecoin more fungible by adding Confidential Transactions." -Charlie Lee