Firstly, I'm not really an expert on marketing, so take what I say as mere opinion not fact.
I think that you should be pitching it a little differently: many people are confused about what your soundbite is actually saying (I also thought it was a file explorer, like all other file explorers I have even used).
Maybe lean hard into a phrase like "Unified file browser; see all files on all your devices, all at once, all the time".[1]
The other thing I would emphasise is that this isn't syncthing. You don't have to mention syncthing by name, but you could emphasise that "Your files aren't synced between devices, they're visible to all your devices".
Too many people who would otherwise use this would dismiss it with "I'm already using syncthing"! AIUI, you aren't syncing files between devices, only syncing file-listings.[2]
PS. For my own use, unfortunately, I don't need something like this. Sorry.
While it would be a nice to have in theory, it just doesn't solve any pain-points I am currently experiencing.
For example, any important document I need to read on different devices is already either in my email, or on google drive. I view movies on Netflix+AMZ+Disney+, I only ever share photos with others, not with other devices that belong to me. It's rare that I look at a file stored locally on my phone and say "I need to see this on my PC", or vice versa. It just never happens.
[1] That came out sounding super-weird: I did warn you that I wasn't any good at marketing :-)
[2] I expect you provide value on top of that, like transparently copy-n-paste between two different devices, even from a third device.