I think it depends on one's goals in learning the language. If the goals are modest (e.g. say a few simple things in standard situations), then knowing a bit of vocab and couple of verb forms is probably all that's needed.
Going beyond that, not knowing noun genders would start getting in the way pretty quickly:
1. It would almost certainly imply not knowing plurals [since patterns for forming plurals heavily rely on noun genders].
2. It would cause declensions getting mixed up [since those also depend on gender]. All of a sudden, understanding who is the subject and who is the object could get pretty hard.
3. It would make it hard to reliably refer to previously mentioned things without repetition.
Does Duolingo teach patterns for recognising genders and forming plurals? If it doesn't, it's absolutely worth learning them on your own. There are a few patterns that cover the vast majority of nouns. There are weird cases and exceptions, but those are relatively few and really stick out once one knows the patterns, making them easier to remember.
Similarly with verb conjugations. Is it she who is doing something, or is it they? Unless the verb is in the correct form, it's impossible to tell.
(I am a student of German rather than a native speaker, so take all of this with a grain of salt.)