Seeing your name in the credits, even at the very end in tiny font, is proof you helped build something real.

Contribution does not have to be central to be genuine. Being listed at all means something existed that would have been slightly different without you, and that is a real fact regardless of font size. Early in anything, small credits are how a record of your work starts to accumulate.

Take the minor role on something that will actually ship rather than the lead role on something imaginary. Keep a private list of what you helped make, with dates. In a few years that list will say more about you than any description of your ambitions.