CC3+ isn't the easiest or most intuitive program out there, I'll give you that. It does require a little effort to learn properly, but once you have the understanding of how it works it is far more powerful and you can to much more advanced stuff than in those simple 2-click programs. But that power comes with a cost of being a bit harder to learn. I won't be arguing against you calling the GUI old fashioned either. But most of the rest of what you wrote is either directly wrong or easily changeable, or happen for good reasons:

I understand why the refresh can be weird, but it is for performance reasons. CC3+ isn't a bitmap editor like Photoshop, and a CC3+ map contains thousands of entities that need to rendered for every screen update. In Photoshop, you just have a grid of pixels (one per layer). You can have things like vector objects and such in PS too, but not the same amount. Everything being an entity you can manipulate has a huge advantage when editing your drawing, but yes, it does come with a performance cost. Not automatically redrawing the screen for every minor edit is the way to offset that.

CC3+ adds things to the correct sheet (equivalent to layers in Photoshop, named sheets instead of layers because CC had layers long before image editors, so they were named sheets to avoid changing existing terminology. In CC3+, layers are just a grouping mechanic, use sheets whenever you would use layers in photoshop) automatically. Exactly how they are added depend on each individual drawing style, some have mountains on one sheet and trees on another, some place them on the same. This isn't decided by the program globally, but by the style. And yes, you may absolutely want to place a mountain in front of a tree, or partially anyway, to let the top of the tree stick up behind the mountain side. Generally, a single run of sort symbols in map fixes any ordering issues you may have.

The autosave prompt is a bit annoying, but you can turn off the propmt form the autosave options and just have it save automatically in the background instead of bothering you.

These things are for the same reason as mentioned above under refresh. White square goes away whenever you zoom/scroll the map as well as when you hit refresh, it is just a temporary artifact.

They do. Again, this is a property controlled by the style, but most dungeon styles have doors and windows that align to the wall, and cut it.

Wouldn't mind a brush, but for forests and random symbols in an area, you have the Fill with Symbols and Symbols in Area commands. Most overland styles have forest drawing tools that uses these commands to fill the area you define with trees.

True, the floating prompt can get temporary stuck until you move the mouse inside the CC3+ window again. Note that if you wish to get completely rid of it, you can turn it off from the program options.

Not sure why you would need this? You can't do anything with the drawing without a command anyway, so that would basically just be ignoring your clicks. CC3+ repeats the previous command when you click without selecting a new command, because that's what you usually want to do. If you really want a blank command, CC3+ has one though, but it is not on the toolbars or menus, because it isn't normally needed, but you can activate it by typing NULL and hitting enter on the command line.

True. I know many would love to have these. But you don't need to type in things unless you want, when you use for example the sclae command on an entity, it is resized just by moving your mouse up/down so you can eyeball the size. Typing is good when you want exact values and high precision though.

You can, but as I said above, in CC3+ these are the sheets. Sheets can be reordered at will, and you can add effects such as transparency to them to change their opacity.

How are they the same? You have the color bar on the left hand side which gives quick access to a subset of colors, and then the color indicator on the main status bar which you can click to bring up the full color dialog.

Where did you get that manual from? It certainly isn't the one provided with the program. The CC3+ manual doesn't really address operating systems because that's irrelevant, but every screenshot in the manual is from CC3+ running on Windows 10.

You can find the coordinates of any entity by using Info -> List on it. But if you use 0,0 as I wrote above both for the origin point during the copy and when you pasting it, you don't need to know the actual coordinates, since what you are basically doing is copying and pasting it with the same offset without caring exactly what that might be.

The Forlorn Cottage style is a very limited Subset of the main SS4 style, and doesn't include things like room tools (The room tools are generally designed for dungeon rooms, not building floorplans like the FC is).

I recommend you just create the map in the SS4 Dungeon of Schley style which is a full-blown dungeon style, which also includes all the tools and symbols from FC.

1. Generally don't overwrite things, make a copy and edit it instead.
2. There are a lot of things you can change from within the program that you could make a backup off, such as Symbol Catalogs (.fsc files, live in the @Symbols directory), Drawing Tools (.dto files, lives in @System\drawtools), templates (*fct, @Templates), symbol catalog settings (.sis, @System\Symbol Catalog Settings), Symbol Catalog Master Filters (.sif, @System\Symbol Catalog Master Filters)
3. No. There isn't a way to reset other than reinstall or restore from backup.

Note that the files you are most likely to change (accidentally) are drawing tools. Symbol Catalogs can only be changed by loading the symbol catalog as a drawing (instead of into the symbol catalog window) something most people don't do and pretty much guaranteed wil never happen accidentally. Same with templates, you need to load these as a drawing to change them, changes in a drawing never change the template it is based on. Symbol catalog Settings are also somewhat easy to accidentally modify, if you click advanced in the select symbol catalog window.

Things that only affect the current drawing are changes to fill styles via the Fill style dialog, as well as editing symbols via the symbol manager. The latter only edits the copy of the symbol in the drawing, and not the global symbol catalog.

Well, things are not that much different. Yes, the miniatures and grid have been switched out by a VTT, and handwritten notes are now done digitally, but we still sit around the table, argue about the rules, and consume tons of snacks. And with a VTT you don't have to have the minis for everything. And it saves lots of space on the table.

I used to be the DM that described the place and had them draw their own maps, but I realized that it took away a lot of the game. Players would spend unnecessary much time drawing, and they would frequently ask me to repeat distances (which I could hardly refuse to do, the characters were there in the middle of the dungeon and could re-check things as often as they liked).

This is why I love the VTT and projector approach. My players only see what their characters see in that moment. It saves me from describing every minute details about direction and distance, but the players see the current situation. I don't let them see back to where they have been, only the exact place they see right now. If they want a map, they can draw it, but I save a lot in explanation, and it looks so much prettier. And I can put in semi-surprises as part of the map drawing. Now, they need to actually use their eyes to spot certain things instead of me describing everything.