As the others have indicated, SketchUp is totally capable of making good and even detailed models for 3D printing but like any tool, you have to learn how to use it properly. Once you do, you can make extremely elaborate models for printing that won’t require any repair at the STL stage. If you want to see examples of models that need no additional work for printing, I can show you some. Here’s one I did this evening to wet your whistle.
The SketchUp model
From the slicer:
