Jan, and many others, have made a lot of valid comments on this
discussion. So why have they all been summarily dismissed with such... complete lack of consideration?
The folks at the foundation are not copying files and running update.php every time they update Wikipedia. :) They also have a focus on foundation-sponsored projects and improving things where their constituents are. Not a lot of Wiki* editors need a better MediaWiki installer.
I don't believe it is much of a priority - for the foundation or a significant percentage of third-party administrators. Those who are dedicated figure it out, new people have to have a lot of patience - or they are turned away. Which is really sad, IMHO.
To that end, what can we do about it? Might I suggest we put together an IdeaLab proposal https://meta.wikimedia.org/wiki/Grants:IdeaLab and see if we can pool our own resources (attention and time) to figuring out what it would take to improve this part of MediaWiki? See if there's enough interest, identify opportunities for support (dev skills and money) and take care of this.
I also suggest we make an appropriate and courteous amount of productive noise in Phabricator https://phabricator.wikimedia.org/tag/mediawiki-installer/. Add experiences, feedback, and information to existing tasks related to the installer. Add new ones for issues that have yet to be discovered.
Yours, Chris Koerner clkoerner.com