[2021] Are 'Assets that are missing' still ok to use?

Props and trees missing from a building will only cause them to not be there. The building will load and work just fine, it simply looks different.

Missing networks can cause a building to not load at all, but then that building will show up as broken, so you can just ignore the "missing" warnings and only look for "broken"

Removing assets that have missing dependencies will lower memory usage some - since you will load fewer assets. That might improve performance for some people who have very high memory usage.

Similarly subscribing to all the missing dependencies might impact performance negatively since more assets means higher memory usage.