I see where you're coming from. This website used to just document roller coasters but since merged with another wiki, dedicated to flat rides, so now it covers both. We started with a very broad scope of every ride. However following some discussions, it was decided to omit the smallest "juvenile" rides due to the very large numbers of them, how similar they look and how often they change hands which all made tracking them very difficult. Bear in mind that this was largely from a British fairs perspective. I started the list User:Lachlan/rides to track these, and also track the names of other rides to try to establish a common naming system but it's still far from complete.
The scope can always change in the future depending on what the community wishes for, but personally I think it would be better to focus on the larger rides first before expanding it further.