Its not like star trek you can't just ask for a toy car and you get it. There is a lot of setup leveling and tweaking of supports and the first layer of print to get the print looking clean or even printing at all.
Printing takes hours like 6+ for anything remotely complicated. It will probably take you two or three goes printing a thing until you get results you are happy with. Once its printed you then need to clean up the print removing support etc.
What material you print in will also massively change your results / chances of success. You may need to encase the printer to control the environment temperature, wind and toxic fumes depending on the material need to be accounted for.
The stuff on thingyverse all looks cool but it's all cool gimmicks if you want to do something useful you need to know how to 3d model.
TLDR: It's all a bit of a faff but if you are the type of person that likes to build their own computer its a lot of fun, being able to download a car felt awesome. The toy car has surprising detail and despite being made in PLA the easiest plastic to use its again surprisingly strong.
Ease of use 4/10. If you can't 3d model its fairly useless 1/10. If you can 3d model its so much faster and easier to get complicated parts 8/10.