Visited the Saga Holidays website yesterday to do some research. Hat's off to them. They have obviously been making some changes since I last visited. This website is now a model of clarity, and it makes browsing for holidays a breeze.
One thing it manages to do that many other sites can't is combine different types of holiday for a destination into one, easy to follow report. So, if you search for holidays in Croatia it gives you details of all the resort hotels you can stay at, followed by all the escorted tours that pass through Croatia, followed by any cruises that stop in a Croatian port.
Sounds easy, but most travel websites can't do it.
BTW, the yardstick for online flight booking sites is how well they can cope with anything more complicated than ticketing for straightforward 'city pairs'. Most really can't manage complicated multi-leg itineraries very well.