Wasn't my experience, frequencies are fine but I don't think it's unbeatable at all. The default simulation is 50x speed by the way, perhaps that gave you the impression.
Based on... What exactly? The Dutch rail network is already considered the busiest network in Europe. So I'm really interested what knowledge you bring that says that it could be busier if many experts say that the busiest trajectories (look at Amsterdam - Schiphol and Amsterdam - Utrecht, for example) are at max capacity already.
> but I don't think it's unbeatable at all
Based on... What exactly? The Dutch rail network is already considered the busiest network in Europe. So I'm really interested what knowledge you bring that says that it could be busier if many experts say that the busiest trajectories (look at Amsterdam - Schiphol and Amsterdam - Utrecht, for example) are at max capacity already.