Modernizing these apps seems very high-impact. These are the very first things a new user sees and after the initial modernization, they should be relatively cheap to maintain.
Messaging can be replaced with one of the hundreds decent messaging apps.
Unlike the backup app which is utterly unusable, untrustworthy and frankly crap. And CANNOT be replaced by anything else.
As it stands it's impossible to have reliable backups in GOS.
If my phone were lost, stolen or destroyed, I would simply revoke its Wireguard key, buy a new Pixel, flash Graphene, and provision a new Wireguard key. Essentially no data of value would be lost, and restoring my apps and settings manually would take an hour tops. Admittedly, I don't use many apps, so YMMV.
And I'm syncing some of the app data already, but that is not a replacement for the OS apps.
Most of the data cannot be synced like this.
Isn't it because of lack of the root access?
The lack of root is only significant because unlike in other vendors the built-in backup doesn't work reliably, and you can't use third party software.
But I'm very hopeful, recently they released this Messages update, they're working on introducing native RCS somehow (no idea how but I wish them well), and they recently made a first-class automated call recording.
I agree that a new backup system is also high impact, but there can be more than one high-impact thing, and the Message app is really low-hanging fruit.
Personally I don't need RCS so I simply use Textra since forever as it's far better than Messages, but lack of backup is impacting everyone much more - no other app can be used to back up the OS.