Its patched on the new engines. You could still do it at the start of MW3 with a devkit PS4 and additionally you could do XP/Stat Editing hacks on MW2019 but they stopped syncing XP and progression on P2P because the method was done via force hosting. So, everything is now synced to their server, which means progression and everything else is no longer possible to manipulate.
Perhaps something might appear in Zombies but its way too early to give a definitive answer on that.