"By the time new members were accepted into NATO ... Russia had started its descent into a totalitarian dictatorship"
The decision to expand NATO was made in 1997 [0]
And by the way, here is a passage from wikipedia on that first round of NATO enlargement [1]:
"That year, Russian leaders like Foreign Minister Andrei Kozyrev indicated their country's opposition to NATO enlargement. While Russian President Boris Yeltsin did sign an agreement with NATO in May 1997 that included text referring to new membership, he clearly described NATO expansion as "unacceptable" and a threat to Russian security in his December 1997 National Security Blueprint."
And a bit from "What Eltsin heard" [2]:
"On December 1, Foreign Minister Kozyrev unexpectedly refused to sign up for the Partnership of Peace; and on December 5, Yeltsin lashed out about NATO at the Budapest summit of the CSCE, in front of a surprised Clinton: “Why are you sowing the seeds of mistrust? ... Europe is in danger of plunging into a cold peace …. History demonstrates that it is a dangerous illusion to suppose that the destinies of continents and of the world community in general can somehow be managed from one single capital.” "
[0] https://en.wikipedia.org/wiki/1997_Madrid_summit
[1] https://en.wikipedia.org/wiki/Enlargement_of_NATO#Visegr%C3%...
[2] https://nsarchive.gwu.edu/briefing-book/russia-programs/2018...