For the cops, prosecutors, and defense attorneys, the show doesn't give the proper sense of immense caseload. Each episode feels like they're focused 100% on a single thing, when in reality they're probably juggling dozens, and stretched thin.
The cop side of things in L&O is fairly unrealistic, but imo in more minor ways for pacing than anything egregious.
The prosecutors of course don't get called on 4th/5th amendment violations as they normally would, and my memory is the defendant testifies way too frequently (for homicide cases, in that time priod). And it doesn't do a realistic depiction of the rate at which people get completely screwed over by corruption. And it doesn't do a great job pointing out how often prosecutors will take cases prioritized for their own political careers.
I am not a lawyer, and the lawyers I watched L&O with were civil litigators not criminal litigators, so some of my perspective is probably off (though I suspect in ways that are more favorable to the show). Also it was like 25 years ago? Lol