In the early 1990's I rode Boulder Canyon near Boulder Colorado among other canyons. I weighed 200 lbs and the altitudes ranged between 5,500 and 9,500 feet. I started with road bikes then I came across LBS that listened to what I was saying I needed a road bike with a granny gear like a mountain bike. I wound up with a bike with a 28/28 low gear. It still wasn't easy for me but I was not tearing my knees to pieces. I really miss the climbs but not the descending

If you are bored while climbing you are becoming anxious and wasting energy learn some breathing techniques to relax the anxiety. concentrate on your breathing while climbing and take breaks