Ulyanovsk would complement rather than immediately replace the Kievs

Were two Ulyanovsk-class carriers intended to replace the Kiev-class aviation ships?

No; Soviet practice favored retaining older ships, so the classes would more likely operate in complementary task groups until a later successor replaced the Kievs.

Institutional practice matters as much as ship capability because the Soviet Navy was reluctant to discard usable hulls. Ulyanovsk and Kiev therefore make more sense as parallel task-group assets, with replacement deferred to a later carrier generation.