> Why do developers only work on ticket-sized portions of the actual requirements? To put it succinctly: because they are simply too dumb. They cannot wrap their heads around it. They cannot grasp it.

I think the reason is entirely different: ticket-sized portions of requirements are the only thing that one can hope to estimate in any useful fashion. Business side needs estimates, so they create pressure to split work into pieces they know how to handle.

Put another way, it's not that developers are "too dumb" to wrap their head around actual requirements. They're not allowed to. The business prefers devs to consistently crank out small improvements, keep "velocity", even though it leads to "organically" designed systems - i.e. complex, full of weird edge cases, and smelling of decay. The alternative would be to let the dev talk, design, experiment, take the project holistically - but that also means the work becomes impossible to estimate more precisely than "sometimes next year, maybe", which modern businesses can't stand.