Why can't Zoro fans prove he can deal with FS ?
Katakuri is strong in CQC because he uses FS and logia-esque body to moprh around attacks. AOE counters this style.
Dragon twister from rooftop Zoro has high AOE (size of dragon Kaido, who's town sized), and AOE is a reliable counter against future sight.
Current Zoro can make it much bigger and stronger (see Bird Dance's evolution)
One or two dragon twisters with advanced conqueror's haki is enough.
You can even argue that current Zoro can just straight up tag Katakuri in CQC even. You can count in one hand the number of times he's been tagged clean in 1v1, post timeskip. Zoro has one of the best reflex and reaction speeds.
Absolute worst case scenario, Zoro defends until Katakuri's future sight runs low (his CQC is more than enough to keep defending, you don't need FS for that), and then beats him up