I think there are several reasons for that:
1) The architecture elements such as this one overflowed the market
2) You're using model from the tutorial, there are a chance of someone having the same looking model on cgtrader
3) You're using Blender (not 100% the reason)
The last one is also familiar to me, I'm also using Blender. For some reason the standard is still 3ds Max for most of the buyers (I know you can export in fbx), but you will get sells eventually
I can recommend you to improve your lighting and to try selling on blendermarket