That's like saying you can't receive a recessive gene that produces blue eyes cause there's "mixing and dilution".
And I doubt that every Uzimaki had this powerful chakra reserve, it showed up in a few of them and resulted in some of the most special ninja of the manga. 4 Kage (Naruto, the 1st, 2nd, and 4th), Kage-level Nagato, and the 3 jinchurrikii of the strongest tailed beast.
they weren't uzumaki the 1st and 4th just married to them..and the 2nd never had uzumaki p*ssy, probably never had p*ssy at all...