There are many things to love about Krita but it's often extremely annoying to deal with where it counts. there are some problems that often halt my work and force me to go back to photoshop or sai, for each of these problems I've searched all of the menus and found nothing to fix it. if there is a solution to them, they are too obscure to be useful to the new uses.

1- Can't limit the drawing to the image boundaries.
I'm sure there's some performance penalty for drawing outside of the image where I don't want or need. One suggested solution was binding a key to "Trim to image size" and press it every time I want to delete the pixels outside of the image area, that would be after every brush stroke, seems like a modern car without windshield wipers and I have to get our of the window and wipe the glass by hand while driving.
In my 10+ years of working with all kind of graphic software, I didn't encounter many cases that I needed to draw outside of the image boundaries, we need an option to toggle it on and off instead.

2- Layer thumbnails take forever to update.
Even on a small canvas, it takes like a couple of seconds. That can be a side effect of drawing outside the canvas to the infinity.
"0.1 second is the response time limit if you want users to feel like their actions are directly causing something to happen on the screen…" I suggest fixing this issue since it makes the program look laggy and slow, specially when we do something that doesn't show inside the canvas like "Trim to image size"

3- Thumbnails show what's drawn outside of the canvas,
Even if I select the canvas area to not draw outside, the thumbnails still show where my brush have traveled. It seems like wasted effort when there is no pixels changed outside of the image area and the program shows me a bunch of empty space where my brush would paint something but didn't.

4- The thumbnails don't keep the correct aspect ratio and try to fit everything in a square.
Together with drawing outside of the canvas, often the thumbnails look like a squished mess with a whole lot of empty space around it. A thumbnail that doesn't represent what's visible on the layer isn't that useful.

5- The distort brush doesn't have strength slider.
Full strength is often needed to stretch lines perfectly across some area. It's a bit hard to explain but if you've done precision work, you might have faced the times you needed to cut some part of image, move it, then re connect the lines between.

6- I gave up trying to get the individual HSB sliders under my color selection
Tweaking one of those sliders alone is often used in pixel art. Even if there is such an option or docker, it is too hard to find.

7- I love the wrap around mode, but I was a bit disappointed to see it doesn't have vertical and horizontal only mode for tile painting.
It's still ahead of photoshop and most drawing programs out there with no such option though.
The wrap around mode is the only time I can think of, that I need to draw outside of the image boundaries.

8- The filters are amazing but they often resize the canvas. it's very annoying.

9- Some filters create amazing patterns to use as a base for game tiles but without seamless option, there's lots of fixing needed before they're usable.

10- As a game developer I'm excited to see Krita can export to Webp format, can't wait till the export options for this format are added for fine control.

11- The bug report page needs one line "Post your suggestions here" linking to this forum. and maybe this forum needs a sub-forum clearly marked suggestions.

I like Krita and I think it has the potential to become the one tool that does most of the things 2D game developers need. That's why I would love to get involved in the development but as a designer with limited coding knowledge, I'm not sure where I can be useful.

While we're at it, though this is probably going into a black hole:

12 - When pasting an image too large to fit the canvas, it just cuts off. That's not great.

13 - After making a selection, switch to the Transform Layer or Selection tool automatically. Let the escape key and "deselect all" switch back to the previous tool. This would save a lot of time.

Some lighter issues and thoughts:

14 - Clamp selections to the edges of the canvas once we have the ability to turn off out-of-bounds drawing

15 - The +/- keyboard buttons should still respect the mouse position, instead of zooming into the center indiscriminately.

15 - The file-layer workflow simply doesn't work, I've tried to set up a 3x3 array of a tile-file, it rendered my brushes unusable, after closing the program and re-opening it few times it started working but stopped updating after two times I've saved.
It wouldn't be fair to compare Krita with Photoshop, but we can learn how to make workflow easier for the users. setting up a layer-file can be simplified to
- make a selection
- convert to file-layer
- save file layer
- shift+double click to open it as a document

Of course we have to do all of this because we can't simply select and isolate a part of the image and work on it with wrap-around option. Give this to pixel artists and scrap the whole file as layer idea, if it's not working, it's not working. Don't spend any time on it