The exact same trick works with custom search engines in Chrome as well.
They're equally powerful. Automatically adding search engines means users don't have to do so by hand, but you can still manually create a "search engine" too (e.g. "https://xkcd.com/%s/" with the keyword "xkcd").
In Firefox I keep a folder with bookmarks that have keywords, but I would prefer the UI in Firefox's search engine settings (the bookmark manager doesn't have a keywords column).
The problem is few will discover Firefox's bookmark keywords unless they're told about the feature, and manually create such bookmarks, while Chrome automatically creates keywords for search engines and prompts users to try them out.