Regarding the yearly themes in WordPress: the features being shown off are, hmmm… major. This has been happening for a couple of years, and will certainly continue into WP 6.0, where the entire theming system is undergoing an overhaul. There are now “Classic” themes and Block themes, which call upon different skill sets to approach customizing.
If we separate that from the new user experience, I hear what you say about folks seeing Discourse as a new, constantly updated product that persuades folks to try it.
I’m just kinda personally traumatized as a WordPress developer on what is happening with the themes, how they are tied to new features, and the pace of rolling them out. I’d like to learn lessons from that project’s approach to new themes/features, and apply them in Discourse. 