We have had two flats in about 6,000 miles running Schwalbe Marathon 700X37C with tubes on the tandem. Both were pinch flats, so if we had been running tubeless they would not have happened. One happened a couple miles from home, so no big deal. The other was on a barely there road in the middle of nowhere. We have about 3,000 miles on Continental GP5000 TL 700X32C running tubeless with no flats. That is not much of a difference
Flat prevention is not the biggest benefit I see with tubeless. It is the ride quality and the feel of the bike when cornering at speed. Some of that can be attributed to the different nature of the Marathon vs the GP5000. On my solo bike I find that tubeless transmits less road vibration. It is enough better that when I ride with the tube only wheels I am very much aware of the difference. The only tires I am running with tubes now are either winter studded tires that are not tubeless ready or on wheels that are not tubeless ready.
And for me the "mess" of tubeless has not been an issue. I have had a few flats, but all of them have been larger cuts or ruptures, and the tires were not repairable.