Unless I'm misunderstanding, the Xbox series S is definitely NOT the reason the graphics are sub par, one would need to look no further than the game still releasing on last gen consoles including the Switch.
Take last gen out of the picture and just develop for this gen of consoles and you would more than likely get the graphical updates...hell Madden did it, basically release 24 as nothing but a roster update, so not sure why The Show can't do the same...unless there was something involved with MLB and the porting process stating that the game HAS to stay on last gen as well...