"OpenOffice decided not to have a learning curve"

The OpenOffice.org and LibreOffice office suites have retained a traditional interface that most users (of them or any other office suite) are likely to find familiar and pretty easy to use, without having to learn it or get used to it first.

In contrast, some other office suites, including newer versions of Microsoft Office, have implemented substantial interface changes, often again and again with each version. These changes arguably introduce some substantial benefits, but at the cost of confusing users and making them learn something new. Learning new things is great, but most people don't use word processors and spreadsheet software for its own sake.

While making sure users continue to be able to migrate from Microsoft Office is a substantial consideration that goes into the development of OpenOffice.org and LibreOffice, it's worth taking note that these office suites have deliberately not changed their interfaces to mirror the newer Microsoft Office interfaces. It's more important that OpenOffice.org and LibreOffice users be able to use OpenOffice.org and LibreOffice without interruption, than for people who have only used new versions of Microsoft Office to be able to switch to them without having to figure anything out.

Fortunately, the OpenOffice.org and LibreOffice interfaces are designed reasonably intuitively and they are well-documented (with pretty good help materials), so people who have only used office suites with different interfaces should be able to learn to use them without too much difficulty, even many years from now.

"Firefox tries very hard to make sure pages written in 1995 look like they did in 1995."

The Firefox web browser is written in such a way as to maintain backward compatibility as well as possible with old web content. Not only should old web pages load and function as well as they did with browsers that were current when the pages were created, but they should do so seamlessly (without the user having to enable any sort of "compatibility mode") and they should look as close as possible as they used to look...or at least as close as possible to the way they looked with previous versions of Firefox.

"Windows isn't a poor man's Linux."

Either the reverse is intended ("Linux isn't a poor man's Windows"), or this statement is unclear and needs to be modified and/or further explained. Either way, this should probably be reported as a bug in Ubuntu's community documentation. Perhaps you would be willing to do this? In any case, if we wait for some more answers here, maybe we can gain more insight into what may be intended by that statement, which could help in reporting the bug.

EDIT: There's been a great deal of speculation in comments and answers as to what "Linux isn't a poor man's Windows" means. Several peripherally similar but ultimately different ideas have been proposed. I think this shows even more strongly that this sentence is unclear, and that its current form in documentation for novices constitutes a bug.