Yes you can, by using your computer to download appropriate firmware bin file from Amazon's servers and then transferring it to your PW3.
Code:
https://s3.amazonaws.com/firmwaredownloads/update_kindle_all_new_paperwhite_5.13.6.bin
This is direct link for downloading firmware 5.13.6 ( = the last firmware before UI changed to this new look) for PW3 aka "7th gen" Paperwhite. Use that as a "template" to construct a link that will download whatever version you want , just change the version number.
Before deciding if you want to go beyond 5.14.1 my advice would be to search for discussions about UI changes and functional changes in regards to Collection view / collection sort and library UI in general. Many people seriously dislike those changes.