So I thrashed my storage drive recently. (Expanding and moving a partition. Didn't work, gave me the long overdue opportunity to convert to BTRFS.)
In the following weeks, I've been slowly reinstalling games as I feel the want to play them. Today, was Civ IV's lucky day.

It's just that, to install 4 GB of data, it's been taking a while. As in, it would have been faster for me to unpack the game myself and/or download a fully unpacked version of the game.

Now, I am using Wine, and I am installing to an external drive, but surely this did not go as slowly as when last I had installed.

Is this the garbage I have to look forward to, now that games have been turned into Galaxy streams, instead of left well enough alone? Because that is no way to retain a customer.

The ongoing artificial degradation of post-Galaxy offline installers is something that's been discussed (sadly too many) times before:-

https://www.gog.com/forum/general/offline_game_installers_why_use_ctemp/post17
https://www.gog.com/forum/general/dosbox_linux_support_dropped/post27
https://www.gog.com/forum/general/gog_standalone_installer_is_single_threaded_and_so_slow/page1
https://www.gog.com/forum/general/it_seems_like_gog_is_unable_to_retain_even_their_long_supporting_developers_now/post19

True, but I'd figured that it wasn't this bad; but I guess I'll avoid any Windows installer that involves a bin file from now on. Good job, GOG. You've made me want to avoid installing a game.

If y'all ever get that VIP pass, be sure to take it up with staff on that new and exclusive official GOG Discord channel.

Don't hold your breath though. They only want to hear about new directions for GOG. Fixing anything existing isn't important to the execs.

Here's a new direction: Shut out Windows users, and go full Unix/Linux only.

Another new direction: Axe Galaxy, throw it out the window, along with any documentation, files, or references to it.

Yes, then we will be stuck with the buggy steam galaxy wrapper for all eternity.

Like you suspected, it is indeed much quicker to use innoextract to unpack the game data instead of executing the installer through WINE (or even on Windows from what I understand). So my suggestion is to always use innoextract with GOG Windows installers.

https://constexpr.org/innoextract/#download, which is a command-line program, works on GOG's offline installers and extracts files very quickly.

Innoextract - How to Use

Question: If new installers contain game data in some new "stream" format, then how is it still possible to simply extract files with Innoextract? I don't know the technical details but "Galaxy streams" sounds like a mess of small data chunks which are then "rebuild" (renamed, combined, byte-patched, etc.) into actual files. Or am I wrong with this assumption?

So how long did it take for you in Wine + external hard drive?

I tried installing Civ IV Complete on Windows 11 (the installer files were on the internal SSD and installed there too), and considering the installer is only like 3GB, it did indeed take quite awhile to install it, little under 11 minutes.

For comparison, I also installed Wolfenstein The New Order whose installer is over 10x bigger (41,9GB), and it took 13 minutes, ie. much faster per gigabyte.

So to me it appears there is something abnormal with the Civ IV installer, making it extra slow. At least one thing is that while New Order is a much bigger game, it seems to have much less files:

Civ 4 installation directory: 39 781 Files, 2 918 Folders
Wolfenstein The New Order installation directory: 192 Files, 32 Folders

Another one: based on the Civ IV installer file name, it isn't actually in the newest GOG installer format?

setup_civilization4_complete_2.0.0.4.exe
setup_wolfenstein_the_new_order_1.0.0.2_hotfix_(36443).exe

Didn't GOG start using those "brackets-numbers" like (36443) when they moved to using some newer format of the installers, e.g. the aforementioned Galaxy streams format or whatever? Not sure if the older format was somehow (even) slower?

Also take into account that the installer might try to install some dependencies as well. The Civ IV installer seemed to be "stuck" for a long time in the beginning of the installation, I am unsure if it was installing some extra stuff there? New Order also ran some VC++ and DirectX9.0c installers as well, at the end of the installation process.

So you can't quite directly compare the time it takes to uncompress the installers with e.g. unrar or innoextract, as they don't run that extra stuff. But yeah, I guess the installers could still be speeded up, if that was the main target to optimize them (and not e.g. try to make them be similar to the Galaxy version, making it simpler to maintain the offline installers).

You assumption is correct in that's how it works. The author of InnoExtract updated it:-
https://www.gog.com/forum/general/adamhms_linux_wine_wrappers_news_faq_discussion/post147

Ok, so what would you say is the maximum acceptable time for a game to install, regardless of its footprint?

For me it is 15 minutes, thinking back to how long some games took to install on CD/DVD. Anything more than that is inciting refunds.

Does Civ IV Complete use that same format as well (considering its filename has the older version numbering format, with no bracket numbers)?
Naturally depends on the size of the game too. Civ IV Complete installation is indeed abnormally slow, a 3GB installer taking 11 minutes, while The New Order (42GB) is easier to accept when it takes 13 minutes.

Not sure if it is due to the high number of small files in Civ IV, or that its format is different from The New Order.

I don't know for sure, I don't own that game. A lot of people have complained about abnormally slow install times recently though, but I don't recall seeing much of that in older 2.0.0.x naming convention installer versions. I still have some of those backed up including ones like Tropico Reloaded, Penumbra Trilogy, etc, where they not only install pretty quickly they also install multiple games at once from one installer. It's mostly the newer 'Galaxified' ones that are slower.