Nothing.
Keep it like this and accept the fact that this one race has its place in the championship for history, glory, glamour, for the black and white images from the 50s and 60s.
Because it is a weird and out of time show that embodies the essence of what F1 was and is, and what remains of its mix of poshness and dirty mechanics working all night to repair a car.
It’s romantic, as simple as that. And not every race has to be an adrenalinic circus of overtakes. We could just appreciate it for what it is.
It’s racing history, live, right in front of our eyes.
If one can’t grasp this simple fact he/she has not understood F1, in my opinion.
On the other hand, Monaco is one race, and probably should be one only. What I mean is that you definetely can and should keep it like it always has been, but in the meantime you shouldn’t replicate its formula in 42 other races with city circuits in every other exotic city, only because they offer a bag of cash.
Because if you strip Monaco from its heritage and history, yes, what it remains is a boring race in a cramped circuit. And you get Abu Dhabi.
Not a great idea to try a and make another 5 or 6 of it all along the season.
THAT’s not interesting. That’s boring.
To improve Monaco you shouldn’t change a thing of it, but you should work to let it be the only one weird outlier in an otherwise more racing-intense championship. Quirky and fascinating precisely because unique, and not common.