This is simple yet annoying thing Illustrator does.
It has its own language preferences regardless of what is set by the system.
This can, at times, cause me to change the language repeatedly during application change.
Illustrator remembers the last language that was set, so, if for instance I change the language outside of illustrator, it changes it back to the one that was set before. Sometimes my working method requires frequent app changes, this creates a situation where I find myself repeatedly changing the language.
The workaround is, obviously, to go back to illustrator and change the language there.
This is annoying and unnecessary.
I think that Illustrator should "respect" the system setting for the current language preference, or at least to have a toggle within it to choose any of the two behaviors.

To fill in my drawing outlines or an object, I have to select the section of outlines or shapes first, which is dumb, because in selecting the outlines or shapes, the color fill automatically changes to the color whatever is selected (the color of the stroke or shape's outline, that I want to fill in with a different color. This is made even more frustrating when I have to use the eyedropper to select a fill color, only for my color section to immediately change, upon reselecting the shape outlines I intended to fill in.

It is also a pain that I seem unable to use the live paint within paint brush stroke outlines, unless the lines are switched to pencil lines or flattened.

Maybe I just don't know how to properly use the tool. Instead I have to always color in my pictures with filled shapes I make from brush strokes, rather than the live paint bucket tool. I feel like the tool needs a major fix to make it simpler to use.

Artboard tool does a lot of things: selects, creates, moves,.. we are out of modifiers to control it properly. Specifically, we can’t create square artboards with the natural way we can create square paths, circles with Ellipse tool, like in many applications.

Instead, Ai uses Shift key to select artboards if you start holding Shift before clicking (which is fine) and uses ratio of the last selected artboard if you hold it while dragging (who even uses it?)

What if you let us to create square artboards, when no artboards are selected, but Shift is held? The alternative is to get rid of proportions lock completely.

Please also take a look at the related request: https://illustrator.uservoice.com/forums/333657/suggestions/34561711

We have to work with a strange legacy dichotomy when making a selection in Layers is NOT equal to making a selection on canvas and vice versa.

No other vector application does it like this:
XD, Affinity Designer, Corel Draw, Figma, Xara, Inkscape...

Other apps which have layered structures don’t do this also:
Photoshop, Blender, 3DS Max...

InDesign and Illustrator are lonely black sheep in the flock of apps.

We need a mode (as an option) to be able to sync both selection methods.
Clicking an object on canvas should highlight the name of it in Layers.
Clicking a name of an object in Layers should select this object on canvas.

Extended reading:

These two selections are like the dark matter and the normal matter — they don’t influence each other and can’t be converted into one another.
Here is the request about it: https://illustrator.uservoice.com/forums/333657/suggestions/32505679

When an object is selected on canvas, Layers does not get expanded to display it, and we have to click the tiny button to see it in the document structure.
Here is the request about it: https://illustrator.uservoice.com/forums/333657/suggestions/39104935

Yeah, we can wrap it an an action and spend a precious F-keys to robotically press it after each selection, which is twice dumb, because an action which has only one operation in it is a bad action. Every command in Illustrator should be assignable to a hotkey.
Here is the request about it: https://illustrator.uservoice.com/forums/333657/suggestions/31609237

And also we have three places to click in Layers to select an object:
1. Names, largest and most easy to click areas — clicking does nothing to select objects though
2. Target buttons, small circles, which are in fact just indicators for the custom appearance applied — clicking them both targets and selects an object, all their children (except locked and hidden), and it’s the only way to select objects on canvas via the panel. Also it support selecting ranges with Shift held — after we begged for it for 3 years (here is the request about it: https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests/suggestions/19196674-select-more-than-one-layer-at-once).
3. Selection markers, which are indicators too, but again can be used as buttons... but without the ability to select ranges with Shift. In fact, Shift here works as Ctrl/Cmd should, and Ctrl/Cmd does nothing. I have no hypothesis why. Markers can be displayed as small and large, meaning partial (some children are selected) and full selection (all children selected).

You can read about these columns here: https://helpx.adobe.com/in/illustrator/using/layers.html
Note that this article says nothing about the dichotomy.

Finally, I can see why the current approach can be useful. This allows us to put some objects in an existing group, to reorder, to move to another layer, to switch visibility or lock in mass — via a stupid dialog... without messing up with what is selected on canvas.

Is it worth the hustle though? This can be done with a context menu for Layers panel (here is the request about it: https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests/suggestions/31956982-contextual-menu-with-layers-palette-same-as-phot) with 'Lock selection', 'Hide selection', 'Isolate selection' (for objects from different groups, here is the request about it: https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests/suggestions/31540384-isolate-selected-objects-without-having-to-group-t), Copy, Group/Ungroup, etc.