No, you can't say that in general.
If the addon for example is not actively maintained it could be that it's not actively used anymore (neither by the dev).
As long as noone tries if it works AND then reports any occuring error, and does "not" get any feedback on that for at least 2 months then,
you cannot say it is abandoned.
You can only assume that, but thats you on your own, silently, without providing feedback. And that does not help to fix any addon
It also for example depends on how many addons the author got to maintain, if the addon is a real addon or a patch the dev did to fix it for another dev (who came back then and fixed the real addon so the patch was obsolete meanwhile), and so on.
If you want to know if any addon is abandoned: Ask in the comments or via private message to the author.
No response for several weeks (at least 4): maybe abandoned. But the author decides if it actually is abandoned or not.