I totally get your concern!
For ready-made assets, check out BIMsmith Forge and BIMobject.
They offer extensive manufacturer libraries so that save you time from building from scratch!
But if you're looking to automate creation and placement, try Dynamo!
I used it before to quickly generate about 70 unique door types.
I would've gone insane if I was manually creating everything!
My biggest tip is to refine the details after creating the base designs.