I assume you mean the treeline in the background. They are mostly brown because shade intolerant species are generally self pruning once the canopy closure stage is reached. For the unfamiliar, this basically means that lower branches don't get enough sunlight once the trees in the stand grow tall enough to shade them out and they die. This is a pretty typical growth pattern for most conifers. Some of them are all brown because they aren't used to getting that much sunlight and are basically the tree version of sunburned. As far as natural old growth forest being uneven aged stands, that is a pretty sweeping statement, and generally a wrong one for a lot of if not most shade intolerant species. The natural succession for conifers (and some others) in the west is a catastrophic fire take out whole swaths of forest. But the trees are ready for that and have mechanisms to reestablish themselves after the fire. Some of them actually depend on fire to open up their cones and release seeds, so fire is necessary. Then a whole even aged stand of timber grows in place. Way too many tree by modern standards. We thin out trees and sell them for pulp in the south to reduce the number of stems per acre, but the USFS generally practices natural regeneration. The way that works is eventually the stronger trees choke out the weaker trees and the weaker ones die. In the south they make a snag and provide habitat for a lot of animals and bugs and stuff until they fall down and rot. In the west, they just kind of hang out and create fuel ladders until another fire sweeps through and starts the whole process over. Done properly, clear cutting mimics this natural process and instead of converting the wood into carbon dioxide, it sequesters it into the walls of the houses built out of it. Obviously done properly is key here, but do you really think a bunch of USFS employees who have dedicated their lives to growing sustainable forests because that is something they love are just gonna say screw it, let's just turn it all into a moonscape?