The housing crisis in the west is largely not a lack of land or places to build, but an issue of building being too onerous for a variety of reasons.

Inaccessible lake homes being allowed to be used as a primary residence will not fix it.

There is a reason for it. Infrastructure, access roads, public transit stops, build quality, utilities. The Netherlands has very high standards for homes and the direct surroundings and these homes do not meet those criteria. You would also have significantly more emissions if people started living there which would go against the emission limits for nearby nature.

Let me guess, no sewage disposal.