Taking a train to the nearest (usable) airport within the Netherlands takes between 2 and 2.5 hours depending on the available trains, amount of transfers, and "high-speed" (not actually) rail surcharge. Actually, because of a train hitting someone, I currently can't reach any airport by train because my city is right at the edge of the train network. Groningen-Schiphol is similar, and Maastricht-Schiphol is 2,5 hours at the very minimum. Meanwhile, Amsterdam-Brussels takes about 2 hours.
Our regular train speeds are 80kmh to 140kmh, with maybe a little bit of 160kmh on specific stretches.
I realize my country is incredibly well-connected by public transit and those 2 hours are already a massive luxury compared to probably most of the world's population, but I wouldn't mind a few high-speed lines from the center of the country (probably Utrecht) to major cities. With trains currently being more expensive than taking a car if you travel with two people or more, it'd make the high cost worth it.
and your country is 320 kilometers high and 250 wide. There may be a lot of problems with your rail network but insufficient train speed ain't one of them. With the current rail speeds you can cross it comfortably in two hours in any direction. Probably you need to optimize it, lay new train tracks, but there is no need to go for the expensive high speed.
The station density in NL simply doesn't allow for the same kind of high-speed rail that you see in Spain, France or Germany. The segments Groningen-Zwolle and Maastricht-Eindhoven are basically the only parts where train speeds over 200km/h make any difference. On all other trajectories, the limiting factor is not the maximum train speed but the interference from other rail traffic.
The major cities (Amsterdam, Rotterdam, Utrecht, Den Haag) typically have 4 trains/hour going between them. Higher-speed trains won't make any difference there, unless you first build out dedicated infrastructure (like the IC Direct line between Schiphol and Rotterdam, which cuts a whopping 20 mins from the regular IC travel time).