This is an excellent general assessment of what greatness is, but it's worth noting that doing this is easy in an amateurish era and nigh impossible in a professional era.
That's why Magnus Carlsen is the greatest chess player ever and Wilhelm Stienitz is not. There's a difference between battering elite professionals who've trained all their life and between being the guy who owned everything by discovering the basics. Dick Fosbury isn't the greatest high jumper ever, even though he beat superior athletes with the technique he invented. Grace was a great man and a pioneer, so was Bradman and so was Sobers but it's just orders of magnitude tougher to be ahead of everyone else in a professional environment in a mature game than it was in 1885 when being professional was an insult.
I agree with you as far as you have gone in this post.
Where we disagree is on the period from the Golden Age (1890) onwards. The dawn of the Golden Age in 1890 being when players started to play 15+ First Class matches per season.
Because those cricketers were in my opinion MORE professional and better prepared for Test cricket than the players of today.
Let's look at David Warner. He is soon to be 29 years old. He has 12 centuries and a Test average of 47.29 after 37 Tests. So far, so good.
But he has only ever played 55 First Class matches in his entire life. He has only ever scored 5 First Class centuries outside the Test arena. At the age of almost 29, in other words, he has 17 First Class centuries in 55 First Class matches. And it is in First Class cricket that you learn to play against slip cordons and on deteriorating pitches against spin bowlers.
Which, of course, is why Dave Warner has lost 6 consecutive away Tests to India and Pakistan. He is not a hardened professional, superior to those of earlier generations. He is a gifted novice.
Compare with, for example, Gordon Greenidge of the West Indies. Every season apart from international cricket he played:
15 x First Class matches for Hampshire, against the world's best bowlers like Bishan Bedi, Richard Hadlee, Imran Khan, Joel Garner et al.
6 x First Class matches for Barbados against the likes of Andy Roberts, Colin Croft, Michael Holding et al.
3-6 x 60 over Gillette Cup matches for Hampshire
3-6 x 55 over Benson and Hedges Cup matches for Hampshire
15 x 40 over John Player League matches for Hampshire.
3-6 x 50 over Inter-island matches for Barbados.
It is absurd to say that Dave Warner is a more professional, more highly skilled batsman than Gordon Greenidge was. He basically plays a fraction of the top class cricket that Gordon Greenidge did, and at the age of almost 29 has less experience at First Class level than Greenidge would have had when he was 5 years his junior.
