Pearce was a good signing for a couple of years, Barnes was a good signing for a season too. And I was talking about the cornerstones of Keegan's team, not the additions. Lee, Ferdinand, Ginola, Beresford, Albert etc all over 30 in Dalglish's first full season.
Bottom line: Dalglish did some good things here. McClaren didn't.
Ultimately your bottom line is a key point, and I agree with that, but Dalglish did more harm than good for us IMO. The three most important players you've mentioned above (Lee, Ferdinand, Ginola) all went on to have a good few more years playing very well so they could have remained cornerstones.
He did sign some good players but certainly didn't himself get the best out of a large number of them. Speed in particular was shocking in his first season for us. Hamann was the only thing I remember loving about that period of time.