You can think of Bases as an editor and visualization layer for the YAML frontmatter in your Markdown files.
Frontmatter is not part of the original Markdown spec, but it became a standard way to add metadata to Markdown files long before Obsidian came along. I believe it started in 2008 with the introduction of Jekyll:
https://tom.preston-werner.com/2008/11/17/blogging-like-a-ha...
Frontmatter is supported by almost all SSGs and many apps like Obsidian add autocomplete and other QoL features around it.
Bases to me is exactly what you describe. A feature that provides an excellent editing environment and extensibility for Markdown files.
For example, my blog is a set of Markdown files compiled with Jekyll, that I edit in Obsidian. Now I can add a base in Obsidian that helps me see the state of different blog posts/pages, quickly sort/filter them, and edit their metadata. It helps me spend more of my time editing Markdown files, but at a higher level.