Yep, and as far as I understand, nobody has said otherwise in the answers here.
Also, Fossify and Etar are pretty much the only free and open-source calendar apps out there, or at least that I’m aware of. Of course, if you don’t care about that, there are lots of proprietary calendar apps in the Play Store, some of which might have CalDAV built in — I’m not sure.
Ultimately, however, the DAVx5 ↔ calendar app combo is the better and more flexible solution, because, as @DuffyCloud has already explained, DAVx5 then syncs the Nextcloud calendars with the calendar database on your phone, and any tasks and calendar apps can then access this database.
Oh, and just in case anyone is put off by the cost of DAVx5, which I think is worth paying for if you can afford it, there is a free version of DAVx5 on F-Droid: DAVx⁵ | F-Droid - Free and Open Source Android App Repository.