Yes and no. Going full send isn’t the magical answer to every question and situation. For example, Japan can throw everything it has got against China in a new Pearl Harbour attack, and all that will achieve is make them loose faster and harder.
The answer you seek is the very philosophical core of warfare, and the world’s greatest minds have had a stab throughout history to distill it into simple rules like the famous Art of War and innumerable other works.
The reason Iran is punching so well above it’s weight in this instance is overwhelmingly down to American arrogance and negligence in not having done its own homework and prep work properly beforehand, and having terrible leaders making terrible strategic decisions far more than Iran going into supersaiyan beast mode somehow.
America prepared half-arsedly; didn’t bother to build a coalition of the willing; made it crystal clear to the Iranians that they have no choice but to fight for the very survival of their nation and people; and got baited into wasting its alpha-strike taking out a 86 year old religious leader who was already dying of cancer and his hand picked list of all senior Iranian faction leaders most likely to be traitors or useful idiots for America and Israel.
In doing so, America gifted Iran the kind of internal unity of purpose none inside Iran could possibly achieve themselves, and ended up being the one who’s military was caught on the hop in the most critical opening exchanges. So rather than dealing a hammer blow to the Iranians and fundamentally degrading their combat capabilities, it was the Iranians who managed to systematically take out US sensors and communications networks in the region to massively degrade their early warning capabilities, thereby having a cascade effect on both missile defence interception rates and air bases sortie generation rates.
The Iranians can now fight without fear or hesitation, because they have the clarity of purpose that comes from knowing there won’t be any other battles if they loose this one, so they don’t need to complicate their thinking with saving strength for the future wars to come. But that’s a very rare and unusual thing, so their strategy isn’t directly transferable to most others.
It is also due to logistical issues and force composition. Japan can't actually full send with its military, since they don't have anywhere near as many strike assets as Iran has and is too far away from China to have the effect that Iran has. Japanese force composition was dictated by the US to be a mostly air and naval control asset, while they provided the offensive strike power.
Better comparison is North Korea, which
does have a Iran posture with its force composition and geographical advantage, and yes, it would absolutely devastate South Korea if it does go full send.
They really underestimated Iran, but what more could they have done?
Take another 6 months to build up more THAAD and Patriots when they have ~20 THAAD radars total in the world and Iran took out 5 in a week? When Iran can pump 100+ MRBMs alone per month?
Send more aircraft... where? They withdrew aircraft and personnel from UAE, Bahrain and Qatar because they didn't want them being taken out on the ground.
Send more carriers... when 7 of them are in maintenance so only 4 are available?
Put more ground forces... to do what? Staged from where?
This is the same problem as what they face against China. Yeah "buy more THAAD" - and put them where that wouldn't be redundant, when there are only 20 systems ever made? "Put more aircraft" - where that won't get taken out in round 1 of strikes or even on the ground to a preemptive strike? "Position more carriers" - from what inventory?
Iran just stopped responding symbolically and giving warnings. This is what Iran always could've done all along, they just didn't because fighting a superpower sucks and you'll take losses. It's just that now they have no choice.