The unions not only brought about direct actions on the employers they work for, they also brought about legislation, regulation and awareness for employees of other employers. The only way to evaluate the effect of companies alone without the role of unions, is to look at an era where unions didn't exist.
Just because your employer didn't have unions, did the laws of minimum wage, overtime, 401k matching or the like in the jurisdiction not apply ? Did employees become unaware of the possibility of unions just because the specific employer didn't have unions ? Did they stop having options to move to employers with unions ?