How are you actually proposing that they fix this issue? Simply set the software to automatically downgrade the quality of an image (without changing its dimension) to match some arbitrary file size?
I've tried doing that in Lightroom when I had a photo I wanted to use for an image background on some online service which restricted file sizes and I needed the image to have specific dimensions to fit the required space. I was quite unhappy with the results - especially for higher resolution files, the quality decrease required to try and fit the file size for those dimensions was huge.
The thing is - for other photos it would be much less of an issue. That's the nature of digital photography - depending on the specific image being captured, you can get vastly different results for compressed file sizes.
You also generally want to avoid (lossy) compression of PNG files - I use them for screenshots where you need the retain the sharpness of the original image and JPG's lossy compression would make the image blurry and difficult to view.
So in this case I think I agree with Chris - it's not really a trivial thing to fix and is likely best left to an external service to optimise your images. I don't think that arbitrarily downgrading the quality of images to hit a target file size is going to give satisfactory results.
I'm not sure why you are so against resizing images? Consumer level digital cameras are taking 20MP photos these days - you simply don't need that level of resolution for displaying those photos online - resizing the images down to a much more reasonable level (perhaps HD or even UHD) will achieve the file size reduction you're seeking.
If you then want to further optimise your images for performance, look at the 3rd party image optimisation services available.
What do you think happens now when you upload an image larger than the allowed image dimensions? It gets resized and recompressed. That's how a smaller file size is achieved.
The compression part is different for each image format and should be adjustable, naturally. But this is on the admin side, it should be up to the admins to specify how exactly compression should be handled (e.g. turning off chroma subsampling), with some sensible defaults applied.
The specifics of how individual admins want to handle certain file types are up to them. I for example can't allow people to upload lossless PNG screenshots when they end up being cca 5MB per image because a) it's a complete waste of space, b) unnecessary and c) a few dozen such screenshots will fill up every users' quota, which is obviously frustrating for the users as well. This will be the same for most admins, but any with unlimited resources can simply not apply any image size restrictions and deal with the inevitable consequences.
I'm assuming that you're not very familiar with image compression because JPG doesn't have to be blurry or have any visible compression artifacts at all. It all comes down to the compression level. As long as the compression setting is low and chroma subsampling is off, any jpg can look the same as a lossless format. Most if not all digital cameras output JPGs and they're obviously not coming out blurry.
This is pretty basic stuff and not at all complicated. Even anyone completely unfamiliar with it all could learn about it with the help of a manual entry or a short FAQ/guide.
Apparently you don't understand the issues we're discussing here, it also seems that you haven't read the previous thread.
I am not necessarily against resizing certain images, but not all of them globally with no alternative, as I have to do now. Resizing images is not always desired or needed (e.g. game screenshots, not every image is a digital photo like you're assuming) and also many images can be smaller in size than the arbitrarily set global max image dimension for XFMG images but still be way too large, e.g. PNG screenshots that I mentioned in the other thread. What somewhat works for one image format (jpg) does not work at all for another (png).
