I've used vintage 2x5, 3x7, 2x9 shimano, 2x10 shimano,2x10 campy, 2x11 campy, 1x14 rohloff, all at length. Personally my favourite is the 11sp. I do appreciate that extra gear. We are like motors in that we all have our own optimum rpm, and much like a car, we work better when in our optimum gear. Now for some of us, 2x5 is all you're going to need.

But you can't then generalise and catagorically state that it's all anyone could ever need. More gears are not necessarily a bad thing or simply a gimmick to make you buy more schwag (they could start making 2x5 groupsets for weight weenies and still sell it!).

Just like more gears are more efficient for a car, they are for us too. Or at least, they can be.

FWIW I ride 11sp but the single speed I have gets the most use