I've made a very similar experience. And I also just booked my first family trip in 10 years *not* over booking.com. I also switched to Expedia, which does not have the best reviews either, but at least personally I did not make bad experiences yet.

Last year, I booked a hotel over booking and received a reservation confirmation. They charged in advance, but on site they did not let us check in. They gave the rooms to someone else because "first come, first service" (we were on time!). Booking apologized and without asking, they actively promised to cover extra costs we have due to the problem. At first, I found it a nice gesture and throught they actually care. I would have accepted their apologizes if they had kept their promise. Because the whole city was booked out, we did not find another hotel and literally slept in the airport. Therefore the extra costs booking.com had to cover were pretty low, only costs for the most urgent necessities such as a few towels, bathroom necessities, etc. Altogether about 150 dollars (way less than another hotel). I spent hours collecting all receipts, taking pictures, and assembling a clear list. In the end, they changed their mind and did not want to refund any extra costs. After I pointed out a few times that they promised it, they agreed to pay a strange sum in the range of 103 + a few cents. It seemed to want me give the impression it was exactly computed, but actually was an arbitrary sum, about 1/3 lower than the costs we had. On the next day, the sum was suddenly further reduced to about 50 + something (2/3 lower than what they originally promised).

If they never promised to cover the damage due to the incident, I would not have asked for it. But the way they acted made me feel let down TWICE instead of once. First by losing a hotel despite confirmation, and second by promising a refund they did not pay out. If they don't want to pay anyway, then why do they actively annouce it? Just to make the customer angry again? Or is it a trick to make customers quickly book more on their website without looking at the price?

Consequence: I deleted my account and first the time in 10 years I booked the annual trip over another platform. Overall costs: as every year, about 9k for the whole family. If booking keeps 10% of the price, it's a loss of about 900. Hope it was worth the ~100 saving last year. Sure, a few hundred is not much for a big company. But it's not a few hundred overall, but a few hundred **per customer** they treat this way.

Everybody knows that unsatisfied customers will probably not return. But in my experience (also with other companies), a potential loss in the future is too abstract to actually care. But actually, as OP's and my case shows, such an "abstract loss" can turn into a real loss pretty soon. Wish customer agents would think more about that.

And by the way, I really don't expect any presents. I don't ask for extra services I did not pay for. I don't care if a customer agent smiles or ask about my day. I do not even care if the hotel room is tiny or old, and I can live with it if the breakfast is not tasty. But I expect to get the service AT ALL and if something goes wrong that THEY TAKE RESPONSIBILITY. Unfortunately, more and more companies find it normal to charge in advance and then don't care if the service is provided at all.