I think this is a tradeoff to not using any centralized service for notifications. I feel you though. I remember Matrix Element battery drain was so terrible I uninstalled it too.

Not sure when it was that you used SimpleX, but there have been many improvements. They have three options for notifications with varying battery drain:

-No notifications: no battery drain

-Periodic notifications: some battery drain (every ten minutes)

-Instant notifications: substantial battery drain

I'm content with periodic notifications, but understand why that wouldn't be enough for some.