My utility bike has a relatively upright position with short reach and it is exceedingly comfortable and can easily be ridden in normal clothes.

For short trips.

I sometimes wonder whether such a comfortable bike would work for touring and then comes the day when I have to ride more than 15km with it and I decide no, there's absolutely no way of making that thing work for me on longer trips or touring.

A few reasons why:

1) upright position puts most of your weight on your saddle, which then requires an exceedingly good fitting saddle to avoid any issues. Some people have that dialed in, but I suspect most haven't to a degree an upright riding position would require.

2) as leaning forward more to an extent helps holding up your torso, leaning forward also allows access to better muscle recruitment. That can mean many things for different people and I can already hear the "I'm not in a hurry" -crowd stirring, but it's not really about speed. It's about fatigue avoidance and efficiency. Climbing a hill is harder with insufficient muscle recruitment. You'll also be slower but also more tired. So there's that too.

I used to have a dutch style bike where you sat bolt upright and it would have perhaps worked for touring in the netherlands if daily distances were under 10km with breaks and with a good tailwind. Climbing anything with that bike was a complete non starter as you could not utilize any of the muscles in the back of the leg.

this may come out a bit strong but leaning forward is how optimally cycling is done. A moderate lean forward (around 45 degrees back angle) is the most comfortable position for long distance riding just like a heavy forward lean is the most comfortable position for long distance xc skiing or a good straight posture is best for long distance running.

But it still is what it is. Cycling isn't like lying in bed so you're going to develop aches and soreness like in any sport. The deciding factor is whether they are below the toleration limit or not. If not, they are an issue meaning something is wrong with either bike fit or rider and needs to be addressed.