The main issues with the old Cross-Class system were that the 'scavenger hunt checklist' for essential actions were distributed entirely across older jobs, and several of the choices were downright bizarre, like being able to bring across GLD/MRD's Savage Blade and Skull Sunder over to classes that could not utilize them as combo actions in the first place. The former is the reason why some jobs, like DRK, were hit significantly harder by the transition to the Role Action system in Stormblood.

That's not to say that the Role Action system isn't without issues either. I don't really understand the design philosophy around why Rampart was specifically designed as an Role Action when you have Sentinel/Shadow Wall/Nebula with identical wording to each other. Likewise, I don't see why Reprisal was a Role Action when you also have Dark Missionary/Heart of Light with identical wording to each other in the same category. It feels like the dev team themselves are unsure of what the point of this system is, outside of occasionally saving on having to create new animations for the same action across several jobs.

Perhaps the solution is to just introduce slight variations on a theme, and allowing players to unlock new animations and modifiers on a Role Action when they start up a new job. For example, perhaps Rampart is the base action, but unlocking it on DRK lets you use the Shadowskin animation and alter the properties to trade off recast vs. duration or flat DR vs. % DR. I think if it's not specifically designed to allow for player choice and fight-specific optimization, then you're better off just scrapping the system and just duplicating the actions across every job so that we can at least have unique animations for these actions.