Maybe they're comfortable some places, but they're a ridiculous piece of clothing the majority of the year in the US. Living in Atlanta, I've made it a goal to wear a suit as little as possible as I find myself hot/sweaty in all but the deepest parts of winter.

I feel the whole concept of a suit is quite out of place in a modern world where climate controlled buildings are the rule rather than the exception and most business/frufru social events happen within them.

I feel the opposite.

I wonder how anyone could wear suits before the advent of climate control to keep the inside of buildings cold even during the hottest summer day.

Tropical weight worsted, seersucker, linen, all work pretty well. Tropical worsted in particular is what I steer my friends towards usually as it looks about the same as a normal worsted but is much cooler.

I have worn plenty of well fitted suits. That said, none are true bespoke, so I can't comment there. I love suits, but for comfort's sake, a hoodie or a looser unstructured cotton jacket wins just about every time.

I've worn both entirely custom-made suits and off-the-rack ones. All suits I've ever worn have the same problem - the standard sorts of fabric/design that everyone recommends for "a dark suit" is too hot and doesn't breathe enough so you tend to get all sweaty and gross and want to get out of the suit as soon as possible, regardless of how well it fits. In the summer, it's too hot outside to wear a suit; in the winter, it's too hot inside to wear one. Hence: inherently uncomfortable. Maybe if you wear one long enough you just learn to get used to it?