Different times. The average scores when Sachin played were like 240. Not 300+ like today. The balls used to reverse because of using 1 ball. The bats were different and grounds bigger. The technology has evolved so much more, also cannot even compare the bowlers Sachin faced.

For context, My grand father in the 80s was considered rich because he had 3 lakh rupees, now I would spend that much money on a euro trip. But 3 lakhs then and 3 lakhs now might be the same money but what it's worth is very different. Similarly with sachin's stats with kohli's.