I wouldn't say that. Aron can used to beat more than just Murkrow and Swirlx (which alone is pretty impressive, since they are very dangerous) Aron can beat Fletchling, Meowth, Porygon, Spritzee, Pawniard (lacking breaking break), Vullaby, Snover, Taillow, Zigzagoon, Archen, Foongus, Torchic and Lickitung.
This is not a small list, in fact Murkrow and Swirlx are both S-ranked threats and not a lot of LC pokes in A-B rank can say that they shut down two S-ranked threats. Spirtzee, Murkrow, Vullaby, Pawniard, Foongus, and Porygon are on a large amount of teams in this metagame alone.