Well I'm not a huge fan of messy clutter, and I find it annoying seeing my room in a mess or tripping over stuff that's laying around. I kinda like to keep things organized. Not to mention I'm in here all the time, so when looking around it seems only natural to think "how can I improve this, or make that better?" I sleep on a couch rather than a bed to save space and make the room look nicer, I got a bunk bed to have my pc under and use the bed section as storage area, while walling it off with uniform figma boxes so you can't see the stacks of random boxes. Also helps that I blocked off the windows and store stuff in their place.
I guess it helps to be good at organizing and packing stuff too? I try to maximize the space available to me and do as much with it as I can. You could say there's also being willing to toss/sell anything you don't need. People tend to hold onto a lot of crap and garbage without even realizing it. I think moving as many times as I have has helped me with that. Try digging around in some of your old stuff and while being logical about it ask yourself "what do I want with this thing? can I ever use it? does it have any value?" May find the answer lies in your trashcan or a yardsale. I mean I wont pretend I'm not a bit of a pack rat myself, but there's no reason why you can't hord stuff and keep it neatly tucked away.
Besides, hasn't always been this way, I used to live in real clusterfucks of ugly rooms. I think it helps to move and start over again from a blank canvas and have a chance to plan where everything will go. Gotta make do with what you got too. Display cases and shelves and what not help, but they aren't exactly free. I'm not trying to brag here but getting better and better things over the years while removing the old furniture and junk helps.