If you have reused addresses, you have already negatively affected your privacy.
Not necessarily.
Imagine if you and I had a
private deal and you gave me your address and I sent you 3 payments on 3 different occasions. As far as
the rest of the world knows an arbitrary address received coins from 1 to 3 [sending] addresses but they don't know if that address belongs to you. Consolidating those 3 outputs doesn't change that either.