The videos I’ve seen are of the pagers exploding and someone standing less than a foot away being unscathed. Incredibly sophisticated and precise.
(Also, even if you hit the intended target, it's a summary execution of people you may suspect, but who haven't done anything, yet, and may or may not have become active in any hypothetical future.)
And this is war, you are applying impossible peacetime standards. To put things in perspective, a rocket attack from Hezbollah killed a dozen Israeli kids/teens on a football field in July, with zero Israeli military targets impacted.
And it's not a full-fledged war, yet, as illustrated by the fact that the targets were still in their civilian settings. Generally, this may backfire quite a bit, as in a massuve influx in recruiting. (If the same happened to the US and reservists were blown up by some obscure vector amongst their families and while shopping, what would you expect? Awe and accepting defeat?)