This very matter is discussed in depth by Mathias, in Chapter 9 of his The Stength of Mac Lane Set Theory https://www.dpmms.cam.ac.uk/~ardm/maclane.pdf. There he shows that to prove "for all $n$ there exist $n$ pairwise nonequinumerous infinite sets" requires some use of unbounded Separation, and to prove "there exist infinitely many pairwise nonequinumerous infinite sets" requires some use of Replacement. He also discusses various refinements in connection with formula complexity and stratifiability.
Whether or not these assertions count as ordinary mathematics, I find them considerably easier to grasp than Borel Determinacy.
Meanwhile, some of the motivation of this question resonates with mine in posing these questions:
When must it be sets rather than proper classes, or vice-versa, outside of foundational mathematics?
Can one exhibit an explicit Kuratowski infinite set without invoking Replacement?