Refinement is much improved in the 2021 (including engine noise and ride quality), and the low-end power is much better. I think it was @LS500-18 who mentioned how you'd sometimes pull out into traffic in the 18-20 LS and stomp the pedal and nothing happened. That's fixed in the 2021 (and really should be a free ECU/TCU update for the 18-20).No V8 option (while all competitors have it), cabin space (packaging of the platform), refinement (turbo lag, regression on NVH to last LS), being marketed as sporty (but it is neither as sporty as 7er nor as comfortable as an S class, just go with one lol), hybrid model very underpowered (plus the rubber banding weird sensation and high revving noise, iForce Max should solve it probably), technology and infotainment still leaves a lot to be desired. A long list to improve upon for sure.
I don't know how you define sporty, but the 5LS drives like a car half its size on twisty roads. I maintain you can't understand the car until you fling it around some curves for a while, even though that's probably unrealistic for most owners. I'm lucky enough that the shortest route for my daily commute is very curvy, and that's one of the reasons I really like the 5LS in spite of its faults. Driving a 4LS on the same route required more effort and was occasionally terrifying, by contrast.