Slava-class cruisers did have internal subdivision

Did Slava-class cruisers have no internal subdivision?

No; they had internal subdivision, although its arrangement differed somewhat from Western designs.

The Soviet arrangement differed from Western practice but still divided the hull internally for survivability. Ships built since the 1950s commonly rely on subdivision to limit missile damage. That design feature is separate from reported problems such as engines operating far beyond their intended service lives. Sparse or inconsistent public data on Soviet ships should not be turned into absolute claims.