That's a great question, I would say:
- return of the ball trails from 19, so you can actually distinguish the ball from the infield dirt when you're playing 3B
- also from 2019, show a few more balls traveling down the line, even if they go foul, geez add a little suspense
- better judgment on pitcher relief so the manager doesn't freak out when you're up 2-1 and somebody gets a bloop single on you in the 7th
- allow you to contact your agent when times get really tough
- allow you the option of letting the AI manage your running when you get on-base, I find that difficult and tedious; in the alternative, eliminate the huge lag when changing directions in the baseline.
- add real game accomplishments to Events & Awards, like 4 HRs in one game, Perfect Games and No-Hitters
- cut down on the team personnel turnover that seems to get worse the longer you go into the future, where it seems from one year to the next only one or two daily starters remain
- make available more statistics for your past RTTS seasons - for example, you should be able to access league category leaders and award winners, as well as the World Series results and your team's record, back to 2021
- make it so that the other teams' pitchers don't hit 30 points higher than the other hitters against me
- allow more scoring when the human player gets on base, the AI seems to prefer strikeouts, popups, DPs and an occasional walk once you get on base
- get those guys who waggle their bats out of my pitching meter area!
- leave the hitting info up longer once you leave the box