Nonsense. A Citabria is a perfectly fine aerobatic platform. You're not going to compete in Sportsman with a 7ECA, but you can do almost all inside maneuvers with perfect adequacy. As far as power, people do aerobatics in gliders, which have even less power than a 150.
Super D is fun. Pitts is fun. Great Lakeses are fun. But don't you dare dis da Citabria.
~Foxeh
I saw a Citabria competing in primary category at Delano last year: https://iaccdb.iac.org/contests/446 The scores aren't that bad after all; however its unlikely to be any competitive at Sportsman level.