Yeah I have to say it seems like a waste of effort and space. :/ Nearly everything you've made that's custom isn't even noticable.
That is because most of it are near, or straight conversions of BSP brushes.
There exist this neat thing called t-junctions in Source which makes me unhappy.
In fact, I had to delete around 70% of the func_detail brushes in order to go under the limit.
Obviously, this would have left my level a barren wasteland of boredom.
So, to keep up the visual fidelity, roughly half or more, of the original detail brushes were converted into or replaced by simple models.
All the stairs for instance, are models.
I don't feel any of the assets are wasted, even though some of them looks just like a collection of BSP brushes put together.
It made me able to build a world with this level of detail without breaking all the limits of the Source engine.
While still maintaining at least a hint of performance.
I set my own computer as the low to low-medium standard.
It was built in 2003, so you can imagine how awesome it is today.
A big file size doesn't automatically mean "waste of resources" "over complicated" "5 FPS when playing".
It just means I made my own assets instead of using Valve assets.
Many of the custom maps designed are using only Valve assets, so I chose to stand out, and create my own world. (Mostly)
(Do you have any idea how large Dustbowl would be if you zipped all the models and textures used, and released it as a stand alone map?
I bet you it would be well over 200 MB)
Why do I need to sacrifice creativity for a bit of space on a 100+ GB disk, which I'm sure
most have nowadays?
It's a pain to download when the server changes maps. That's all.
If people won't bother downloading it, they are free to do so.
The real issue is, what is faster to render. A model polygon, or a BSP polygon?