I’ve seen thousands of SketchUp models from thousands of SketchUp users over the years and one thing I’ve seen over and over is a model that has added external content that has much more detail than the creator realized.
This bloats your model, slows down SketchUp, slows down rendering - its just not something you want to do!
I recently refreshed my free plugin Goldilocks that tries to help with this problem. What it does is rank the elements in your model by how face count divided by the volume of the element. If you have a tiny little feature with 1000s of faces in it, it will come out high up the ranking and may be a candidate to add to a Layer/Tag that you wish to hide when rendering for example.
Goldilocks makes no choices, it just gives you the information for you to choose.