I think OpenBSD comes the closest to what you want with its two easy to use syscalls that provide syscall filtering and restricting access to paths:

https://man.openbsd.org/pledge.2

https://man.openbsd.org/unveil.2

A few random examples:

https://github.com/tmux/tmux/blob/c8494dff7b6b9a996866edaf8c...

https://github.com/openbsd/ports/blob/master/www/mozilla-fir...

https://github.com/openbsd/ports/blob/master/www/mozilla-fir...

To get the best isolation you need to patch the source — the application needs to go through initial setup and then drop privileges to the absolute possible minimum. But it's easy to make custom wrappers for third-party applications — the above profiles taken from the OpenBSD ports tree are the proof.