You can zoom in a little bit by clicking on the photo:
But you can’t zoom in easily all the way, which I agree is annoying and another reason why I add IDs through the Identify interface instead. To view the full size image from the web uploader, you can click the photo, then right click on the photo pop-up and select “Open image in a new tab” or “Copy image location”, then change “large” to “original” in the URL
"
Hmmm, people should always be able to upload observations without IDs, so if you can provide some steps to replicate that error, please file a report in Bug Reports. More info on that here: https://forum.inaturalist.org/t/about-the-bug-reports-category/60