I moved from syncthing (and seafile) to nexcloud because I was missing one key thing: the ability to share files (by providing an URL, or to a group (think common files with spouse)).
I use Seafile and it has the feature to share to other users on your Seafile instance and to create a public link for uploaded files requiring no account. Is that what you're speaking about? I tried Nextcloud about a year ago, I spun up a Nextcloud and Seafile instance and Nextcloud was much slower for uploading and downloading files.
Syncthing is awesome for being a dropbox-like service for computers. I've setup a syncthing share as a folder inside of nextcloud which is enabled as "External Storage." This gives me the best of both worlds. Sharing between computers is rock solid. The mobile use cases is a lot more reasonable and I can share files.
I don't like syncthing on mobile because it needs to maintain its connection to sync and therefore drains battery. Also, there isn't a way to have less than 100% of a particular share local to the phone. This isn't usually waht I want on my phone.
Yes, it does work with Nextcloud - and this is the reason I moved to Nexcloud from Syncthing (and previously - Seafile).
I was just commenting on your migration to Syncthing, which is a superior syncing app IMHO. It is just that when I was using it I realized that I am missing the share ability, which is avalable in Nextcloud, though my (somehow unhappy) travel the other way round from Syncthing to Nextcloud.
I think that Nextcloud is trying to cover too much things, with half-baked apps.
Otherwise I completely agree with the sentiment.