I don't worry about weight. I feel no difference in my 35 lb. bike with 20+ lb. of water for a day ride vs. loading up with 110+ lb total bike and gear.
I'm not a flatlander though. I climb all the time, every ride. I have no choice. I was amazed one comment I read someone posted a century with less than 200 feet of climbing. I climb 700 feet just the last 4 miles of my daily ride from home. I rarely climb less than 1000 feet on a 10-20 mile ride. I'm not a spinner when I climb, can't do it. I grind. I have way more power to push than I have stamina to spin on a hill. More weight just means I'm a little slower on the hills, that's all. I'm already slow so cutting my 3 mph down to 2 mph on an actual hill doesn't matter much. I do consider anything less than 12% just a slope. Most of my hills are between 12 and 16%. I can sit and grind that all day long, just not very fast.