The only other protection card I could find that removes threat from any scheme and not just the main scheme is True Grit, which might remove the same amount of threat on average but doesn't give any defensive advantage. That makes this a noteworthy card for Protection solo play, which struggles with threat removal, especially on side schemes. Not Today! is comparable to several other protection staples: Never Back Down, Desperate Defense, and Jump Flip. Each has their own advantages and depends on your hero and what scenario you're facing, but Not Today! has its own niche against side schemes. I'm not thrilled about relying on this as your threat removal, because you'll often want to remove side schemes on your own turn instead of waiting for the villain phase (if it has an acceleration icon, for example). A play pattern you can do that's good against a crisis side scheme, for example, is to thwart it down to 2 on your turn, then finish it off with Not Today! in the villain phase before the extra encounter card gets dealt.
I'm still not a big advocate of solo Protection decks built around defending a lot, but if that's your jam, you'll probably want this card!