Better than nothing is the whole point. N95 masks are not a substitute for avoiding exposure in the first place, but nobody’s saying N95 masks are ineffective because of that fact.
The recommendation here is assuming you have access to something better. If you have no access to something better, a homemade mask is better than no mask at all, until you can get something better. As others have pointed out here, it’s rather odd to suggest we should scoff at this imperfect solution, when there are no perfect solutions short of 100% full and complete quarantine, which is completely unrealistic.
