CurlFtpFs is old and unsupported. It can't even copy files with a "#" in the filename.
https://alternativeto.net/software/curlftpfs/about/ says it has been obsoleted by LUFS, but LUFS seems to be even older (2003)!
Is there anything better?
I found AVFS, but I am not sure it is usable with Vifm. There are some old instructions for rox though.