What is the name of this spider I found in The Netherlands?
I believe you are looking at a spider mite of the genus Anystis or Tetranychus. Both of these have The Netherlands in their range.
Here is an info page on the two genuses, includes a map of observations and a gallery of photos that you can even filter to only view images from a certain range. You can also filter the gallery to group photos into species categories.
Anystis: https://inaturalist.ca/taxa/249515-Anystis
Tetranychus: https://inaturalist.ca/taxa/203334-Tetranychus