My actual experience was to book through them, then have the hotel refuse to acknowledge the booking in spite of me printing out the confirmation. They required me to book a room from scratch directly from the hotel and seek refund from booking.com, which never came. The loops of attempting to contact booking.com, both at the time and afterwards, were extremely frustrating in addition to the actual failures to execute and repay.
My pithy conclusion: booking.com is the rare site that can't become enshittified - because it was that way from the start!
If you do try to risk using a 3rd party booking site, ALWAYS call the hotel directly and ask to confirm that your confirmation number matches what you think you have booked. If the 3rd party booking site only gives you THEIR confirmation number, and not the actual hotel confirmation number, bail. You're probably gonna have a bad time.
I'm a front desk agent - if you don't have a valid confirmation number (and your info isn't otherwise in our system), there is nothing we can do, you don't actually have a reservation with us. Something has gone wrong in the middle. We can't give you a free room based on an email that isn't from our property. All we can do is make a new reservation on the spot, paid that day, if we even have a room available.
Most of the places I've worked don't allow 3rd party bookings, thank goodness.
My first year at the front desk, I had a guest who thought they had a reservation, but neither I, nor the manager, could find them in our system - not at our property or any other property in the park, not on any dates that year or the next. We couldn't match resv number, name, address, phone, email. Nothing. Hours later when I was staring at our short list of arrivals that hadn't shown up, I figured out that the 3rd party agent made the reservation in THEIR name, with absolutely no reference to the actual guest in the reservation (based on some suspicious address/phone info in the booking). I never found out if I was right, but I'm pretty sure that's what happened. I hope the guest was able to get things straightened out when they got home.
Just best to avoid 3rd parties.