It’s no secret that homerun production has exploded the past few decades. Of the top 30 seasons by homeruns hit, just one is from before 1990 (1987). Multiple league expansions have contributed to those numbers greatly, but the rate they are hit has also improved steadily.
League-wide slugging percentages have been consistently above .400 since 1990, aided by the prevalence of steroid use in the early 90s to mid 2000s along with perhaps more scrupulous means like changes to hitting philosophies and an increased emphasis on exit velocity and launch angle.
At the end of the 1989 season, there were 63 players to have reached the 300-homer plateau, by the end of 2023, there were 159 players to have reached it, with Andrew McCutchen and Anthony Rizzo both in close proximity and Aaron Judge within in striking distance.