...Several chess websites provide strength analysis and ever since the very beginnings of chess programs, move strength has been calculated and accepted as a method to analyze the strength of moves played in a game.

Some day in the future (maybe not in our lifetime), I fully expect that you will be able to take the complete game database of for example Wilhelm Steinitz or Garry Kasparov, plug it into the master computer program and get the strength results, overall and year by year for each and every player, and accurately compare the evolving improvements of chess knowledge throughout history for players and computer programs.