You're right, the axis of resistance is not a deterrent anymore. But the damage to Iran itself has been very limited. Iran itself is not weakened but has used the time to further develop its space and nuclear technology and finally received the Su35.
Looking at the performance of Assad, is it really a loss to lose him? Iran already has an opium problem from Afghanistan, there's no need to add a captagon problem from Syria. Syria did nothing to protect Iran and is just a continuous drain of resources. If Syria had become more Shia, it might have become a better ally.
Iran has lost some ability to project power through proxies in Mediterranean west Asia. But that also makes Iran less important to Israel. It certainly doesn't make Iran more vulnerable. Iran was also once involved in the war in Bosnia. That was also a waste of resources for the sake of ideology.
