Between iNaturalist and Wikipedia, for me iNaturalist is the more significant of the two. I use iNat every day, have many tens of thousands of observations, and using it I've learned to identify thousands of birds, plants, bugs, fungi, and other things out there. Now I can name trees, plants, birds, et al, but more than that I understand better how they fit together into ecosystems. Also I've learned a lot of taxonomy which actually helps inform my view of the world a lot. In the process I've connected a lot more to nature, and thanks to iNat (and eBird) I now spent a lot more time doing meaningful things exploring wild spaces and spend less time scrolling on web pages. Wikipedia's invaluable as well, and completely indispensable, but between the two it's been less significant for me actually directly learning about the natural world I live in.