I'm not an expert, but with the current implementation of EU policy I don't think we will see improvements in rail connections that aren't freight or the high speed core soon unfortunately.

This is one only part of the corrective actions needed, the other half is improving regional mobility with trains to compensate:

The Dutch parliament is currently doing everything they can to help eurostar's monopoly on travel to the UK by trying to solve the immigration and customs issue in Amsterdam, but they are doing nothing or not enough for all the other less flashy rail travel initiatives. In clockwise order:

• There is no fast international connection north possible from Amsterdam towards Bremen due to missing track alignments.
• Amsterdam to Arnhem and beyond is being tripled, but mainly for freight. There wasn't even a speed increase to 200+ and I didn't hear much about increasing passenger train frequency.
• Eindhoven - Venlo - Dusseldorf is missing a continuous IC connection and the German side of the Venlo tracks need doubling
• A similar direct train to Köln is needed, either from Eindhoven or Maastricht
• Many more ICE trains are needed that travel deeper into Germany, like Berlin, Frankfurt, Munich, Basel and beyond. They shouldn't all leave from Amsterdam.
• Maastricht to Liege and Aachen should be high frequency IC routes, ideally starting further north in the Netherlands
• Reopen the Roermond-Antwerp alignment for passenger rail
• Continuing from Venlo to Eindhoven in the other direction, new track alignment is needed to connect Dusseldorf to Antwerp, Gent, Kortrijk, and Lille as a new mid to high speed corridor crossing 4 countries.
• More competition in service providers on HSL zuid, why is Thalys allowed the monopoly.
• The through traffic from Netherlands to France should not need to spend so long in Belgium, but that is being improved.

If air travel is then still competitive and bottlenecked on slot capacity, connecting Eindhoven Airport by rail and moving more flights there could help.