Generally speaking, yes, translation edits are a good thing. A post in a foreign language is not appropriate (except on multi-lingual sites) and heading for closure or deletion anyway. Translating the post salvages it.
Automatic translations tend not to do a good job, but they at least allow readers to determine whether there is some value in putting more effort. Even a bad automatic translation often allows people who don't speak the post's original language to determine whether the post should be closed, and to give it tags that route it towards the appropriate audience.
If the post is doomed anyway, there's no point in spending any effort on a proper translation. The automatic translation saves work in that case, so it's useful.
A good translation is the very antithesis of a radical change since it doesn't change the meaning of the post (indeed, it's one of the very few cases of edits that literally “clarify the meaning of the post (without changing that meaning)”). Even an automatic translation is an improvement, as long as there's a note that the translation is uncertain; it would be nice in that case to provide a link to the original revision inside the question, e.g. a footer stating
(automatic translation from the original French)
which makes things easier for a competent visitor to provide a proper translation.