There are so many operators. We travel, but do most of our tours ourselves by using a self drive van. Only I drive usually, but lately our son drives. He's not bothered at all with LHD.
Only when this is not possible we use a travel operator. One example was the South Americas. We did the Brazil part on our own, self-drive. Thereafter we organised a private tour using a Brazilian travel agent. The issue was that the van could not be handed over in the other regions. We travelled up to Ushuaia which needs getting into Argentina and Chile. It's quite far to backtrack to Brazil wasting valuable time to return the vehicle. The tour took 5 weeks including five internal flights. We covered the Amazon from Brazil as well as from the Peruvian side before getting to Cusco/Machu-Picchu.
Also the Africa and Chinese tours was by using an operator. Anywhere in Europe, USA, Japan etc we always drive on our own. It's so easy and way cheaper than travel agents. You get to see the places that you like to visit. The accommodation is cheaper too, when you have the vehivescle you select a place a bit out of town at a much lower rate.
We are planning to visit Uzbekistan, Tajikistan, Kazakhstan, Kyrgyzstan & Turkmenistan (The Central Asias) in April. This is difficult to organise by ourselves and my wife is talking with several travel agents in Uzbekistan to organise the complete tour.
PS: Switzerland is quite easy to do by using the Swiss railways.