Why on earth is that the program developer's job and/or duty? If the user (stupidly) wants to run a program completely un-sandboxed, that's their right. If they want to run all programs by default somewhat sandboxed (which is quite reasonable), that's also the user's right and their system's job. Not of the original developer who made the program.
But if you want to run some other program sandboxed, I've heard that "podman run --network=none" works reasonably well.