Most of MEW users are looking for this answer. You can still your old wallet with your private keys in mew website. But you can not same in mobile MEW Connect app & MEW chrome extension.
I've posted a thread about it.
https://bitcointalksearch.org/topic/about-new-mew-interface-apps-and-the-old-ethereum-wallets-5112307
Topic: How to access myetherwallet with keystore file now? (Read 155 times)
Also I addressed the issue about the looks on another reply to someone else :
Yup, Etherscan and Myetherwallet both were updated to a sleeker looking version. However, I find the new design not easy to get used to. I didn't like the old design but I don't love the new one either. Who knows maybe it'll take some getting used to...
What part of the new Etherscan that you don't like? I found it quite appealing tbh. As for the MEW, some users can't find how they can export their private key anymore if they use a keystore, so they need to use the old version to do that, so I kinda agree that the new version is beautiful but need more improvement.
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New interface from MEW looks great but it feels too much of details when compared to old one,in the previous one we only get the simple steps with just words on it.But for accessing the wallet you need to have the backup of file.
If anyone is too fond of MEW they could get a backup of their wallet from any other wallet service (offline/online) and then import it into MEW again - this is assuming they didn't back it up from MEW's old interface in the first place.
Also I addressed the issue about the looks on another reply to someone else :
Yup, Etherscan and Myetherwallet both were updated to a sleeker looking version. However, I find the new design not easy to get used to. I didn't like the old design but I don't love the new one either. Who knows maybe it'll take some getting used to...
snip
New interface from MEW looks great but it feels too much of details when compared to old one,in the previous one we only get the simple steps with just words on it.But for accessing the wallet you need to have the backup of file.
Hello. How to access myetherwallet with keystore file now? 
Same as before.
First
Second
Third
Fourth
Select your File and hit Continue
Fifth
Enter your password and access your wallet.
Like I said, its the same as before...
Hello. How to access myetherwallet with keystore file now?
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