Unfortunately the only real competitive difficulty level is superstar or HoF. Playing on either is not fun (for me) because regardless of sliders or roster edits defense is absolutely the most ridiculous style of play I've seen in many, many years. The most realistic style of play as far as the cpu not mind reading and reacting as you input controls is rookie. Even on Pro you'll see a player with his back to the play, literally react to a drive or a pass as it happens.
There are other under the hood/bugs/factors at play also. For example I am one of the people that really complained a lot in the perimeter defensive thread and came to realize that despite having updates, roster changes, etc my game is playing much differently than what I see in vids and clips. I've actually had it play pretty decent and then, utter crap. Since the last update defense has been toned down, as has the warping and defensive sliding and other nonsense. It even played pretty well for me, but it's reverted back to not being able to move. Currently on default rookie, roster edits with everyone having every single drive, offensive badge and 25 ratings for defense abilities I can't blow by a single person without it taking up half the length of the court. If I get by a guy on a pick, he'll warp from 7 feet behind me to strip me mid layup or float in mid air, in front of me to attempt a block. I've uninstalled it 3 times and only once has it been ok, but I get roster updates and then it's beyond horrible again. There's also speed issues. The game, even without being online at all, will play differently from last time you turned it off. Last I played I had speed, acceleration and anything movement related set to so low it's alarming and it still played fast as hell. Tried reinstalling last night because I have time off for the holidays and default speeds is playing slower than the other day when I had everything down to next to nothing.
The game game is a mess. For lack of better terms, the 'base defensive model' is horrible. Individually most NBA defenders are at a pretty severe disadvantage because, well that's how life works. Defenders have to react and can't break physics to compensate. In NBA 2K24 defenders are just absolute psychic, physics-defying titans, even with ratings as low as they can be. In the NBA a guy who gets the ball on a fast break doesn't slow down despite telling his legs to run as fast as they can, and when a defender sees him break he doesn't warp in front of him and essentially cut off forward momentum.
Just play 23. It's a better game, objectively. It has much. much better player movement and ball movement. Simple plays like a quick screen or pick and roll actually play out pretty quickly. The level of physicality is toned down in a much more realistic manner. All of the cool dribbling is awesome in 24, but if you're like me and have a version where despite updates sliding and defensive absurdity is still present, they are essentially useless. Pretty looking, and fun to use in 2KU, but in game it's just another animation to play out while your defender just mirrors your movement.