The file syncing is not very good either. It's based off WebDAV and very slow. If you only have a few files it's workable, but it isn't competitive with Dropbox, SyncThing or any of the popular alternatives.
I've noticed issue with older hardware. After a recent upgrade to modern hardware (LAN based), all performance issues have been resolved. Currently serving to >30 devices, including 4K media to multiple endpoints and 100Ks files.
It is also workable if you have more than just a few files. I sync several GB of data, books, papers, notes, photos, videos, etc. Constantly changing and it has been pretty fast. Webdav is just the interface used for external services that support the protocol. Which may not be the best tech but it certainly is supported by many, many apps and services. I cannot connect a random e.g. pdf reading app with Syncthing and maybe not with Nextcloud directly but certainly via webdav.
