Why is it the worst way? It would make total sense to combine those ideas.
Typically the user should be primed, given reason for what the notifications will entail, how frequent they might be and so on. It makes users much more receptive to them if you tell then why they should want to have this optional feature enabled, rather than a blind notification popup in first launch.
Right - a popup at launch with useful context rather than a blind "We want $ALLTHETHINGS".
Exactly - I just meant not the default popup as soon as you launch without any explanation or justification.
This is what developers would do in the past with location access also, but as privacy awareness takes hold people are far more likely just to deny these permissions.
In iOS it's a pain for a user to actually reenable the setting after the fact.
Generally speaking, this is the worst way to do it, as the app hasn't made a case for why it needs to send notifications.
It should do it in a contextual way so the user understands that notifications will enhance their experience of the app.