everybody who has a retirement plan is a capitalist because retirement funds invest in stocks, bonds, etc.

The term you're looking for is petite bourgeoisie: people who do get some income by owning slivers of the means of production, but who also have to live by selling their labor. Someone who has investments purely for retirement purposes is straining the lower bounds of that definition.

Everyone with a savings account is a capitalist

Change in your pocket is not anywhere close to owning the means of production.