Honestly, coming from Vero, i find hashtags a pure mess. Full of duplicate and they bloat the UI, which is now clean and focused on the image.
Also, I find the category system we have now a lot faster and easier to categorize the images. By introducing hashtags the current categories become less useful because users could add a photo into a landscape category with tons of unrelated hashtags.
If we really want extra ways to tag images, there should be official tags and not user-made made. If custom-made, at least they should be suggested by analyzing the image (like Vero and EyeEm)