In the beginning, there was ownCloud. They were a good FLOSS offering that decided to start catering solely to corporate customers in the hopes of juicy support contracts. The community who had been contributing the majority of the code gave them a mighty "Fork you" and created NextCloud.
That was about ten years ago. I haven't looked into ownCloud for the last seven or so, but it had stagnated pretty badly by that point. Maybe they've gotten some fresh blood since then, but you'll likely find it to be quite lacking in features and plugins comparatively.
That's interesting that they refactored it. Maybe there have been some improvements made over the last seven years.