Outside of a few that have made their way into Gutenberg in recent versions, I have not been particularly ecstatic about the default patterns the development team has included. In my mind, most were always test cases, patterns meant to iron the bugs out of the system. Then, some of the world-class designers we have in the WordPress ecosystem would design a handful of solid default patterns.

Hi Justin. Thanks for your thoughts on this, I also feel very strongly about patterns and their potential! You are correct the initial patterns included in the plugin were meant to test the APIs and interface more than anything, that's why now upon the decision on which to include in core a few are being taken out. I'd classify patterns into two groups: those that offer convenience (already assembled columns, multiple buttons and images, etc) which can be more mundane and those that offer neat design starting points. I would also like to see more of the latter and feel we are barely scratching the surface on it.

The lack of good and diverse imagery that could be bundled has been a bit of a challenge for designing broader patterns to include in core. The overall quality of these designs would also color the first impression of WordPress for many users, so I feel it's important to put a lot of craft into them going forwards and be confident in their quality. One advantage is that the nature of patterns makes it easy to iterate on them — update, add, remove — building up towards a better collection. As you also said, I do expect themes to push this whole frontier forwards — already seeing some bundling more design-opinionated patterns fitting with their aesthetic, which is really cool. As to which would be bundled in core, I think it's going to change over time, similar to how the default themes change, and as we learn more about their use. Once we get into the next cycle of default themes for this decade, I'd expect each new theme to also contribute their own patterns and experiment more with the feature. It'd be great to incorporate more design diversity here as well.

Perhaps once a directory for patterns can be fleshed out, core might not ship with many patterns itself leaving it more open to designers and theme folks to contribute and curate through the directory and with much shorter cycles than core releases can afford. It's also the case that some of the more opinionated ones have been a bit unrefined in design or structure (even for the Testimonial one, which is going back and forth, it's not great that the markup is relying on a Paragraph block and not on a Quote block, so wouldn't want to promote a pattern that might lead to users having less semantic output).

Finally, please, do keep this feedback going! It's super useful to see what different people are finding more compelling or useful among the bundled patterns as these are still being discussed for the upcoming 5.5 betas, where the broader testing and feedback loop should help decide which to include.