The new upload page is designed so you can see the full image and the tags at the same time. The most basic requirement of uploading is that you should be able to see the image while you tag it. The old page failed at that.
it's still the same as before, when I open related tags I still have to scroll up in order to see the image, plus this should never be a problem for anyone who understands the basics of uploading, anyone who's lazy enough to where they can't upload accordingly simply because they can't be asked to use the wheel on their mouse shouldn't be uploading to begin with.
The commentary is hidden behind a tab because most of the time you don't need to see it while tagging, and because showing it takes up at least half the screen. Screen space that could be used for tagging instead.
a pointless change seeing as the screen is still taken up by the tag box and related tags when open, plus in the old layout you could simply collapse the commentary box when finished with, not to mention the box would automatically collapse if the commentary was added automatically.
Similar images are behind a tab so you can see the full image and the similar images at the same time, and again so they don't take screen space away from the main image and tags.
another pointless change seeing as similar images are there simply to show you that the image you're looking to upload has already been posted, therefore the argument that it takes up more space is completely pointless, and on the occasion that the similar image is different, you still need to open the image in a new tab to view both images at 100% in two tabs in order to see any missing details, and if a user needs to see both images side by side in order to tell whether or not their the same or not and/or whether there are any changes between the two then perhaps that's a personal issue on their part.
You can click the "..." in the top right and choose "Dock to bottom" to put the tags beneath the image like before.
which has just made the reason for the change redundant, another thing is when the boxes are to the side instead of below, the image is forced into a smaller resolution and I can't expand it, thus making the choice of having the boxes below the most beneficial docking, of which is pretty much the same as before but now with tabs instead of collapsable boxes, now I have to alternate through tabs constantly instead of just expanding or collapsing boxes, collapsible boxes are more helpful and less time-consuming.
The recent tags are still there. If they're hidden it's because you have custom CSS or a userscript breaking them.
I don't use CSS and I don't see any recent tags section, I just uploaded before I wrote this part of the reply to check, and there was nothing, I go to advanced settings to see if I did use any CSS code while perhaps I was drunk, and nothing was there, I go back and refreshed and checked again, alas, no recent tags, related tags are there, but not recent tags.
The related tags function the same way as before. Before you clicked on a tag to select it, then clicked a button to show the tags. Now you click on a tag to select it, then click the "Related" box to show the tags. It's the same action.
if it's the same as before then that just makes the change pointless & redundant.
You don't have to collapse/uncollapse the whole box, you can just click the tag name next to "Related:" to update the tags. The difference is that now it shows you which tag you have selected, and all the tags related to it are in the same box instead of in multiple columns taking up most of the screen. This is so it's usable inside small spaces like the right-hand edit panel, the shift+E edit box, or on small screens like phones or tablets.
I've never had to collapse any box when dealing with related tags so I don't know what your point is here because finding related tags was easy, it was just as easy before as it is now, people easily figured out how the related tags work and never needed to see the selected tag in order to know which tag they're looking to find related tags to.
as for the screen space argument, it still takes up space to find related tags regardless, the redundancy speaks for itself.
as for phones and tablets, I can only assume that the argument of screen space mostly applies to them seeing as they have smaller screens to work with, and I can only imagine that the problems I've listed are 10x worse for them as I assume they can't open tabs and have to scroll all over the place just to see glimpses of the pic their uploading even with their devices tilted.
if it were up to me I'd only allow PC users to upload, it's much easier and you're mostly sitting down in the comfort & peace of your own home while uploading, instead of uploading while on loud public transport where you can't think, I'd save you all from that headache.
I suspect a large amount of mistagging was caused by people not being able to see the image and the tags at the same time. They just blindly went through the related tags, clicking on things assuming they were present, not actually looking at the image because it was too hard to scroll back and forth between the image and the tags. This is why it's critical that you're able to see the image while you tag.
"I suspect" meaning you don't know and just blindly assuming, perhaps some people are just inherently lazy and choose not to follow the very basic and easy-to-follow rules of uploading, and the proof IS in the pudding, for example, I ask any mod or admin these two questions, how many times have you told a user to tag their posts because of the lack thereof? and then, how many warnings have you given out to those same users who've chosen to completely ignore your request and continued to upload as they did until you banned them?...just saying, perhaps there are just some people who just don't want to follow the rules, you know, internet trolls.