I agree with mostly everything previously posted, also, the barrels of the bats are thinner than in olden times, another factor in the difference you note.
Not sure if your reference was intentional, or not, but Curt Flood’s suit vs MLB, resulted in the end of the ‘reserve clause’, that broke the bond that teams enforced over players, to one team, causing free agency, hence the reason they don’t tend to stay with one team.
Hope you enjoy the game !