Anything which produces heat needs cooling to maintain an even temperature. What's uncomfortable for you is when your temperature is higher than your natural temperature due to lack of cooling.

that’s bullshit design

We were not designed: we evolved into something that will survive in its current environment just long enough to reproduce, for a number of different environments and despite a number of antagonistic factors.

The fact we generate heat is a really minor issue, in the grand scheme of things, that evolution didn't fix. Were we endothermic instead, for instance, we'd still need to find or create areas of better environmental comfort from hour to hour or day to day. Our fix for the necessity of creating surplus heat through our metabolism or exertion is to sweat. It's our heat sink. It's enabled us to run hotter glucose-driven brains to figure things out better and, thus, out-compete lizards and bears and badgers.

You can hate it, but you do need to understand it's unavoidable -- but it can be minimized, and that is how you cope with it. But I understand the frustration: sweating can really suck sometimes. Sometimes, though - and this is the ironic part - sweating from wild exertion can feel amazing. I bet it's from the endorphins or whatever, and that the sweating is only correlative, but still, good times.