This might be a hot take, especially for LetsRun, but I want to get rid of the 1500m. It just makes no sense on track. The mile is better in every way.
For starters, tracks are almost always 200m or 400m. To get to a mile, it's just 4 or 8 laps + 9m. For a 1500, you have to start 100m displaced from where you want to end, and you get a 300m split and 3 400m splits. That's confusing for anyone who isn't a track buff. Show a random person a 1500 race and they won't have a benchmark for what's fast. If you show a random person a mile race, they can easily see 59s laps and know that it's sub-4 mile pace, which everyone knows is fast.
The mile is 4 laps, starting and ending on the home straight, you get 400m splits that let the audience and runners know what mile pace they're running, and it's not 3 and 3/4 laps. 400m, 800m, and mile races all make sense because its 1, 2, and 4 lap races. So why add a 1500m in there just to make things more confusing? It's not like nobody outside of America knows what a mile is. Everyone knows that 4:00 is a barrier. Everyone knows 4:00 is fast. Maybe you want a marker that is more exclusive than 4:00? Something to seperate college kids from the elite? Well, there's 3:50, which 69 people have broken, and there's 3:45, which 3 people have broken.
The mile just makes more sense to race. Someone who doesn't follow track but turns on the Olympics to see a 1500m race has no sense of how fast they're running, nor how fast is fast. Make the mile great again.