You said it like banking apps will be happy to work with a Linux phone lol, the banks always have their interests inherently conflict with user control anyway. And rooting and getting a custom ROM (one which exists or otherwise) are two completely different things that have nothing to do with each other, and you shouldn't support manufecturers who choose to make it difficult to unlock bootloader anyway.

By 2025, rooting still empowers you to make your own Android device however you like it to be.

Also not many people care about custom ROM these days because Android stock ROM got much better in average, so there's much less a need for creating a brand new ROM just to get basic features. Why making a brand new ROM instead of modding the pretty good one you already have now. And root empowered ROM modding tools that are developed as Magisk module or Xposed modules still have a pretty big community, there's a long list of pretty big repos with hundreds of modules each, and with how sophisticated Magisk and Lsposed have evolved it's easier than ever to write your own mods

Recent AOSP repo added lines of code to Package Installer to handle enforcing restricting whether Package Installer installs an APK file or not based on dev signatures, as well as denying installation if internet isn't available so it can't contact Google's servers for dev signature verification.

So this is enforced by Package Installer, which is already how Google enforces their ridiculous minimal SDK version requirement for installing APK packages, as well as for blocking app update with an APK package with mismatched signature or blocking downgrading an existing app with an APK package, which I already have bypassed via Xposed this way.

Besides, rooting gives YOU total control over your own device like when you have sudo on Linux, even if Google tries some new BS there will be a way to counter it when you have root

XDA is dead, and you just described one of the symptoms of a forum being dead.

That said there are still a small amount of people posting detailed posts for rooting Xperia phones, for how to flash OS updates with unlocked bootloader without losing your user data, for how to bypass carrier restrictions to get international model to work with the 5G bands in the US via build.conf edit and baseband flashing, etc. There are perks of a community being small and niche, and I guess not everyone is brained washed by Samsung's propaganda they use to justify permanently locked bootloader on their phones lol