ADV is not a virus, nor a trojan horse.
> killing the ability to install your own software on your phone
But you can still install whatever you want over ADB...
...if you wait 24 hours.
And also thanks to the new Google Play attestation API a lot of apps won't even work on alternative Android OS'es. But that's all needed in the name of security. Never mind if your Samsung Galaxy phone is EOL and hasn't been receiving updates for 4 years anymore. It still works with the attestation API. But the fully updated GrapheneOS phone is a real security hazard apparently, so it won't work with it.
So no, you can't just run everything you want via side-loading. It's pretty obvious Google is making a power play to curb down on everything that isn't going via Google Play.