Naturalselection – it’s a question I’ve also had. I haven’t seen this answer anywhere but I think the commandment to wipe out Amalek is not that we should forget Amalek (on the contrary the Torah says we must not forget) – like you said we must remember the wicked as a lesson.
Rather the mitzva is to wipe out Amalek’s physical and ideological remnants; whether descendants who embody Amalek’s evil or his ideology – that of denial of G-d’s providence ch’v)