Can’t remember the Louvre, but most places in Europe do that. Covid was a big trigger I think to limit crowd sizes and they manage it more carefully now. I think being able to buy online forces it to be managed too. In the old days, you had to wait on a queue for a ticket. If you can buy it from your phone and everyone converges there at the same time, it’s a nightmare.
It’s a shame though. My first time traveling through Europe in the mid 90s, we could just go with the flow and visit where we wanted with no trouble…walked right to the Colosseum, the Vatican, the main Ancient Roman ruins including The Forum…just show up and enter. A couple years ago we went to Rome for a week during the Christmas break and couldn’t get entry to the Colosseum or the main ruins until the last day because it was all booked in advance. Good thing I reserved as soon as we arrived or we would have missed it. Never got into the Vatican museums so I couldn’t show my son the Sistine chapel (not that he really cared!). Hard to be an explorer when you need to reserve so much.