One thing to note about Feinstein's decline in health is that the reduced immune system response in the wake of Covid infection often results in Shingles flare ups. She ended up getting encephalitis (brain swelling) as a result of the Shingles. Covid->Shingles->Encephalitis and now her death. 

Covid causes spiraling health downfalls. Will her death be attributed to Covid? No, but it is almost certainly part of the story of her decline.