With nextcloud in particular, nextcloud is not just nextcloud.
It's a bunch of additional optional services that may or may not work as-is on Synology. And the Synology package won't come with all of them.
With docker, adding (or removing) additional services, such as Nextcloud Office, is comparatively simple.
I mean... the aesthetic is hot as fuck.
The smell and taste? Beyond disgusting.
So, same. It works in art. Reality, no chance.