Google Play Store review might actually be worse now. It's certainly slower. It's great that you can sideload at least on Android although making money off a sideloaded Android app is very challenging to say the least.

Challenging is better than impossible.

That said, I am left wondering why more major software publishers don't have the option to sideload Android apps. (It was a while since I looked into it, since I mostly use open source apps these days, but it seemed as though most companies were switching to a Google Play Store only route a few years back even though they had the brand recognition to bypass Google's store altogether. The only thing I can think of are support costs, since few people would know how to enable the ability to load apps from other sources.)

You can't get push notifications in a sideloaded app right?

Is that really the case? Why wouldn't you be able to? The FCM APIs aren't gated by install method; I've successfully used them while sideloading my own self-written, unpublished apps.

of course you can. you just need logged off google play services and services framework middleware