We were planing on going to Colorado this summer to stay in the Mountains for a week but luckily did not have anything booked so we are just going to save up this year and go next summer and stay at a better house. IF we had already paid and could not receive the full refund we would go on the trip. But we do not do tourist trap places, we like to rent a house on some lesser known beach or next to some large park and relax, vacation for me is not going to some place and being packed in like sardines.
Summers in Colorado are wonderful. Just remember, the higher up you are going in elevation, the later "summer" really starts. A few of my favorite trails near my house are still closed and/or covered in snow. My favorite trail sits at an elevation of around 10,000 feet and won't be clear of snow for a few more weeks.
If you are looking for isolation and non-touristy mountain areas in Colorado, I recommend targeting places south of Aspen/Breck/Vail. There are some great spots in those towns and some great spots if you go north to Rocky Mountain National Park. But there will be a lot of people. If you go south, there are some equally beautiful spots in the Pike, San Isabel, Gunnison, San Juan and Rio Grande National Forest areas. Crested Butte will have a decent chunk of people, but I don't think I have ever been to a more beautiful location than Crested Butte during wildflower season.