I believe the last feature Krita needs to become a decent design tool would be fixing the layer styles so you can add the same style multiple times to the same layer (and if possible better bevel and 3D text tools). An immense number of designs are not much more than multiple strokes or "slightly" 3D text. Multiple strokes can be done in Krita in a very complicated and impractical way (you can do it by adding the layer style to a group, but with too many strokes the rounding errors make the outer strokes "flat," so the "correct" way would be to add the largest stroke first and then use clones to add the inner strokes). Photopea (a free online editor) supports both of these.

My opinion is that Krita has a tremendous amount of potential to serve a free and open source application for several niche use cases, but it's routinely held back by lacking "that one feature the user will need." Probably because everyone still thinks it's just an application for illustration and can't be used for image editing or design.

Animation is probably the most obvious one. Krita has an entire curves-based timeline editor, but the integration is so poor that it can only be used to animate opacity and the simplest type of transforms (translate, rotate, scale). That's an incredible waste considering it has cage transform, perspective transform, etc. All the non-destructive filters already have the code to serialize their settings to XML and back, but somehow those settings can't be animated? The liquefy transform, by far the most powerful, can't be animated. If transform masks had opacity and you could animate that, even that could be extremely useful, but they don't so they can't be animated in general.

Layer styles are another integration problem. Many users don't know they exist because they're hidden in the context menu. Krita already has filter masks. It doesn't even need a separate UI for layer styles, the styles could just be filters instead, then they would be able to get drag-n-dropped around and you could add multiple of the same to a single layer. Apparently this is because they want compatibility with Photoshop, but you could just convert Krita filter masks into Photoshop styles in the save step, so I don't really understand the problem. Naturally if the filter settings ever became animatable, that would mean layer styles would NOT be animatable in virtue of them not being filters, which would suck a lot.

By the way, I haven't tested the new version yet but Krita ALREADY has a color overlay layer style. So it looks like they simply... duplicated a feature they already had? Also the UI looks very similar to Clip Studio Paint, but a key difference in CSP is that single-color layers use 8 bit pixels instead of full 32 bit RGBA. I'm afraid this UI I'm seeing in the video is going to mislead some users into creating dozens of 32 bit layers with color overlay for easy color management and then end up with much worse performance than they would have in similar software. It also seems the color overlay "mask" behaves in a way that is completely different from literally every other mask in the software. I guess I'll have to download it to know for sure.

Edit: by "3d text" I sincerely don't mean more than WordArt level stuff. A lot of text for mobile games is very basic "curved text + vanishing point 3D + multiple strokes." Krita also lacks a "long shadow" style (i.e. infinite shadow instead of a drop shadow), which is common in a lot of designs and that GIMP has.