I understand that but we are responsible for Iranian lives first. From a game theoretic point of view, if Iran doesn't respond to a violation of its sovereignty, we can expect more attacks like this to follow. The taboo of Israel attacking Iran directly has been broken and if it goes unpunished, it will hugely hurt Iran's deterrence not only against Israel but also against US-backed regimes in the region.
This is pretty much like the situation with Soleimani's assassination. The regime decided to deescalate and it only led to further aggression by the West. In particular, now that Trump is back, a signal of weakness will only lead to further aggression by them.
Yes, Hezbollah is indeed important for Iran. Hamas played dirty in Syria but I would say that Hamas was also an important piece of puzzle against Israel. But Hamas committed suicide with October 7th and it dragged Iran into an unwanted situation without informing us. I still doubt that some factions inside Hamas did it intentionally. I don't trust Ikhwan Al-Muslimin. Both Qatar and Turkey have strategic ties with the US and NATO and it's hard to trust them.