To address your notion of a baseline, professional athletes are defined by the fact that they exceed the baseline. Many of the best baseball players were legendary for having eyesight far superior to the baseline- for being able to see things normal people couldn't see, like, for example, the stitches moving on a fastball travelling at 90mph. So if a baseball player has baseline eyesight, and contacts or eye surgery bring them past the baseline to exceptional eyesight, it might be argued that it's identical to steroid use in unnecessarily bringing them beyond their natural abilities, or it might be argued that it's just bringing them to the baseline for a pro athlete.

Cortisone shots allow a player to play in situations when a normal human being would be in far too much pain to play. Again, it's only bringing it back to the baseline if we define the baseline abnormally. Normal human beings can't run the bases at full speed on a sprained ankle.

As to the sportsmanship argument, sportsmanship is a concept that originated in amateur sports and people have tried to hypocritically and haphazardly apply it to professional sports since their inception, but it has never made sense. The way incentives are structured in professional sports, sportsmanship can only ever be a tertiary concern. The main thesis of the paper I linked to above (which is, I warn, written by 16 year old me and isn't as good as I would write it today) is that attempts to make pro sports adhere to the standards of amateur sports are only ever going to lead to foolish idealists looking foolish, and probably tangentially break other things along the way.