I don't think that is a good choice for the de-Googled crowd, but it will be ok for the Google + FOSS crowd. On a de-Googled phone, there are just going to be too many apps that would have to be on at all times to make sense. But if you are developing for folks that use Google and most apps use the PlayService's Push Notification system, then it's fine.

Ntfy consumes around 1% of the battery just to be connected and receive notifications. If you have 10 apps with their own notification service baked in, just the notification part will consume ~10% of the battery. It doesn't scale very well.