Agreed. For sportscars, I’d say the big enduros are Daytona 24, Sebring 12, Le Mans 24, Spa 24, and 24 Hours Nürburgring. For teams and racers, these are key bucketlist events.
As for layout, its really unique in its still basically the same layout and pavement for close to 70 years. Because of the pavement its bumpy like a street course, but big and fast. Its one of my favorite tracks, but then again I prefer the classics like Sebring, Brands Hatch, Mosport, Road America, etc over the new F1 style courses.
COTA is interesting in that it has some classic US style road course corners (T1, T7-11) but then some artificial modern F1 style corners (like T12-18)