Why can't computer vision identify my photo correctly?

The computer vision suggestions are most accurate for areas with high activity on iNaturalist. It may be that the species you are observing is not yet included in the possible suggestions.

It's also important to remember that the computer vision model is not trained to recognize a certain species—it is trained to recognize typical iNaturalist photos of a certain species. Most photos on iNaturalist are taken with smartphones or other consumer-grade equipment and the organisms are almost always in situ. If you try to use computer vision on pinned insects, for example, it probably won’t work that well because most of the images it has been trained on were of insects observed in the wild.