Ballistic missiles, cruise missiles and ALCMs are good for high value targets yes, however the stocks of them for conducting individual target strikes and re-attack capabilities is much more limited than fixed wing strike PGMs.
In a real conflict, those weapons would operate in conjunction with PGMs, e.g. launch two dozen BMs/CMs/ALCMs at an airbase to significantly degrade their operations, and while their aircraft are on the ground during that time in the next few hours, come in with four strike aircraft each carrying twelve 250kg PGM wing kit bombs to launch 48 weapons at the 48 individual points on the airbase to permanently take it out of action.
Cluster bombs are useful for mechanized forces, yes for interdiction against fixed formations.
Against moving formations, you'd want something able to hit moving targets, including if they are operating in a more dispersed manner.
I think 500kg PGMs have a role, where that much high explosive is just needed.
But they limit targets engaged/sortie, and that is why I am such an advocate for 250kg and 100kg PGMs on multi-ejector racks.
The flexibility, firepower, between two 500 kg PGMs versus twelve 250 kg PGMs cannot be understated, yet both of those loadouts need the same number and type of pylons.
