Comment by bonoboTP

Not sure if counterintuitive or not, but once you have such social mobility-based policies in place ("Your father was a farmer, but you can be a banker, if put in the work") for a few generations, generally people rise and sink to a level that will remain more stable for the later generations. Then even if you keep that same policy, the observation will be less social movement compared to generations before and that will frustrate people and they read it to mean that the policies are blocking social mobility.

You get most mobility after major upheavals like wars and dictatorships that strip people of property, or similar. The longer a liberal democratic meritocratic system is stable without upheavals and dispossession of the population through forced nationalization etc, the less effect the opportunities will have, because those same opportunities were already generally taken advantage of by the parent generation and before.