Please take off the nostalgia goggles. The E39 is not an attractive car. It looks like a generic sedan from the Sims. Boring proportions, and ZERO styling flair.
It also looks hopelessly dated. It looks 20-years older than its successor, the E60. Even if you don’t like the Bangle styling, you can’t deny that the E60 still looks modern today thanks to its flame surfacing. For all his craziness, Bangle brought BMW styling two decades forward in time.
The nicest thing you could say about the E39's styling is that it’s a handsome sleeper. And a sleeper is by definition anonymous and non-descript (read: boring).