age doesn't inherently make math less useful, and the parts it does affect it does non-uniformly.

i have undergone an undergrad differential equations module that taught exclusively ad-hoc methods for certain families of equation that no working mathematician needs to know since they were all subsumed into and superseded by computer algebra systems, but the subject i would enjoy replacing it with (generating functions) is similarly old in origin (perhaps even earlier, since Euler used most of the techniques that an undergrad class would cover before diffeqs were considered an object of study) but has happened to become more useful with the advent of CASes instead of less.