Secure app spawning is a per-app toggle now so it doesn't reduce OS security or the security of other apps without it disabled. It only reduces security of the app with it set to disabled. If multiple apps have it disabled, they share the same ASLR bases, memory tags for memory allocated before fork and other things.

It's one of the toggles changed by the per-app exploit protection compatibility mode. If an app doesn't work, that's the first thing to try. It can then be narrowed down to a specific setting.

The more aggressive exploit protections uncovering a lot of compatibility issues are only enabled for the base OS and specific user installed apps by default. Those can be set to enabled by default for all user installed apps and then people have to deal with the per-app toggles a lot more. This applies to memory tagging, disallowing dynamic code loading via memory/storage and disallowing native debugging (ptrace).