This isn’t good advise. Angular 1.X is discontinued and uses confusing patterns not used in Angular 2 , React, Preact, Vue etc. specializing in it is a very bad career move.
It is a great specialty. Sure doesn't hurt to pick up others along the way, but having deep Angular 1.x specialty 5 years from now will have you flooded with maintenance, upgrade and conversion gigs, and big ones.