Yes, your firm should probably be on social.
But not without first knowing what personnel resources you have available, how you want your firm to be known, the kinds of messages you want to share, and which platforms are a fit for your firm and your audience.
Take it one step further: The only reason your firm should be sharing on social channels is to differentiate your people, your services, and your expertise from every other firm in the marketplace. If you can’t do that, don’t post anything on social channels. It’s not worth it.