It's become really annoying. When I'm looking for where to stay, I find exactly the same thing - the price shoots up once you get to the cart. It's pretty much systematic in Belgium, to be honest, and it varies hugely from one place to another. The fees can be 15%, 20% or even more depending on whether they include the tourist tax, the "resort fees", or just their hidden markups. The thing is, it's not really a standard - some places straight up show you the final price and others play games with it.
You've got platforms like Booking or the hotel chains' own websites that are starting to force hotels to display everything right away in big letters, but it's far from everywhere. You said "I don't like not knowing", and you're right - it's honestly a terrible practice. One thing that can help: some independent hotels or small chains like Ibis or Première Classe often show the real price without too much game-playing. Have you tried calling the hotels directly before booking? Sometimes when you chat with reception they'll tell you exactly what you're going to pay, no surprises.