Yes, mods should close off topic questions. As it currently stands, this site had 13 users with 500+ reputation, which is when you can vote to closevote to close. Three of those users are mods. On a site with only 48 avid users and less than 700 total users, it is important that the mods handle some of the moderation tasks on their own.
Language Learners is a young, small site. Part of being a moderator on such a site is doing things the community can't do yet. Another part is
- Lead by example, showing patience and respect for their fellow community members in everything they write.
A moderator that closes an off topic question is showing that such a question isn't the type of question this community wants. It should be encouraging the users that have the ability to follow the example and close similar questions. Over time, as the community grows the moderators will be able to step back. Language Learners isn't at that point yet.