The point Prabhupada made in the purport to 4.2.31 is that Varṇāśrama is natural. It happens automatically whether you recognize it or not. The system is already in place, we “implement” it by being sensitive to it.
For example, the Bhagavatam describes that the four ashramas are followed in different ways by the four varnas. Each varna takes brahmacarya in a different context and to a different extent, for example. We should “impliment Varnāśrama dharma” by realizing this! Not by expected ever