You may not use it personally, but most if not all Gnome programs do use GVFS, e.g. , Files (Nautilus). GVFS is also used by some other Linux desktops, e.g. LXQt.
KDE programs do not use GVFS.
Rapid Photo Downloader does not care how you mount the device, as long as it can access it and the mount can handle the throughput.
If there is no way to mount an SMB 2 / 3 share on the command line without using cifs that is a limitation in the broader Linux ecosystem, not Rapid Photo Downloader.
If you want to see Rapid Photo Downloader support GVFS directly then that is another matter. That will require a developer implement it, or sponsorship for me to do it. If you are serious about seeing it implemented then organize the support for it.