It’s not a huge problem, but it sucks to find out there’s a problem when doing a routine rebuild, eg for the next version upgrade.
For breaking changes in Discourse Core that affect theme components, we get advisories visible to Admins only for weeks in advance, allowing us to go and fix or remove those theme components. The same would be great for when it’s planned that a plugin will become Core.
For example, I know from this and and linked Topics that Data Explorer is going to be added into Core. That’s great. But I need a decent advisory/announcement on when that happens because I will remove it only when it’s included. Otherwise if I remove it now it risks there being a period of time without Data Explorer.