I will say GrapheneOS is much more usable than normal custom Android ROMs. Maybe this has changed but IME even Lineage based ROMs, official or otherisez don't have automatic updates the same way stock does.

But GrapheneOS and a few similar projects actual have fully automatic updates, for every Android security update and major versions.

Once installed which is very easy as long as your are starting fresh, GrapheneOS requires no effort to maintain. F-droid or even the Google Play Store works just fine once configured. The only apps that don't work are major banking apps and snapchat so not a big deal.

If you have family/friends that use smartphones but don't really use "Apps" then GrapheneOS is perfectly fine.