They actually introduced a shared space at Amsterdam Central Station about 1-2 years ago that I cross daily. The shared space is right next to the incredibly busy ferries and perpendicular to what used to be a bicycle lane. It's now one big square shared by bicycles, pedestrians and scooters.
It does work incredibly well and there are rarely any accidents. The downside however is that it's quite a struggle to cross. It makes me dread to leave the ferry and enter the warzone once again every morning. I understand that it is designed to make me uncomfortable, but it is taken to such an extend that I don't even really want to walk there.
> one big square shared by bicycles, pedestrians and scooters
You mean, no cars?
For high traffic, a roundabout would have to be truly huge. It isn't viable unless land is practically free. You need something more like this:
https://en.wikipedia.org/wiki/High_Five_Interchange
That crosses 16 lanes with 14 lanes. (3,5,5,3 with 3,4,4,3)
But for modest to high volume traffic, roundabouts are better (although if the traffic flow is constant, you usually have to place the crossings a bit further away from the center of the roundabout, which makes it a little harder on elderly pedestrians to go fully "across" since they have to walk the extra distance).