Hi, Comparing a NAS with backup options in iCloud or Google is always a bit difficult. For example, with Immich you can transfer your pictures from your mobile phone to your NAS and access them in a very similar way to iCloud Photos or Google Photos. However, it is an external app that, especially in the case of ios, is not integrated into the operating system at the same level. The same applies to files. With ios, you can only create a backup of your mobile phone manually and then copy it to your Nas.
You can do a lot of things if you really want to and are prepared to experiment a little. But it all involves more effort and less convenience.