This is the 11th review and I'm probably the only one not rating this as 1 or 1 1/2 stars. Here is the problem: yes, Stoclet house is private, yes, it's CLOSED to anyone, but yes: it's great architecture. So a lot of visitors are expecting it to be open, expecting WHS to be accessible. In fact that is not true and was never a commitment by any state party, at least not when this was inscribed. A lot of houses in France and Belgium are private, even some Le Corbusier that were inscribed are not a "museum" for tourists. I once entered the courtyard of the "Fasanerie" in the Potsdam gardens and the lady made it sarcastically clear that "it's private". Mt Kalesh, Tibet, is not to be climbed and yet it will probably still be inscribed in the next decade or so. My point is, just because it's not accessible doesn't make it a horrible site.
In fact, I made it my goal, after reading all the other reviews, to take pictures from every angle possible, checking out each nook and cranny I can see from the outside. It made for a great visit, and yes of course I'm disappointed I can't go inside and see more of it. It would probably be a 5 star site for me! Because frankly if you can't see the outstanding architecture designs and choices from the outside alone then I think you are just not into architecture. I have seen several buildings getting good review for the outside alone, and the inside is shabby or not the original design anymore. Thus only seeing it from the outside is "good enough" for the moment - and you are not exactly going to visit Brussels for just the 5 minute peek at the Stoclet House, right? Also parking nearby was super easy unlike some other reviews have point out.