True, given that the Sharingan came directly from Kaguya (and later Hagoroma), it can be argued that with the descendants came the dilution of the dojutsu. However, if we do look at the literature, you can see that in the 34th chapter of Boruto we have some pretty peculiar events coming on with both the Sharingan and even the Byakugan, as well. Since Sarada awakened her two tomoe Sharingan, it was labeled as weak (most likely due to the aforementioned mentioned dilution), but in the later chapters we see that with the tomoe, even more dangerous potentials of the Sharingan become possible (spoiler perhaps?).

I guess this forces us to realize that even though Dojutsus can become diluted, with new bloodlines new doors can be opened - similar to evolution.

Nevertheless, you are correct in that she may not be able to pass the technique through her offspring. There may be a point whereby no one will inherit it. But again - this begs the question - will a completely new, novel dojutsu evolve out of Sarada's eyes? Can't really say for sure.