It is, but if you are the kind of person these exploits are likely to target, you should have it on. So far there have been no known exploits that work in Lockdown Mode.
You can also selectively turn it on in high-risk settings. I do so when I travel abroad or go through a border. (Haven't started doing it yet with TSA domestically. Let's see how the ICE fiasco evolves.)
If this is a risk for you, sure. Wipe it. For most people they may ask to fiddle around with it before giving it back.