IRBMs weren't the problem. The launches tapered off fast - either due to munition depletion and supply disruption, attrition of launchers and munitions, or efforts to conceal the launchers in face of persistent airstrikes. Either way, the threat was suppressed.
By all accounts, US is much better at "Scud hunt" now than it was back during the last attempt at it.
One-way attack drones? That's a new threat, and one US is far less equipped to tackle.
But I don't think that "OWA threat" was where US strategic planning has failed. From the outside, it seems like US plan was to make a single decisive strike, and negotiate with cowed Iran from there. Iran has failed to be cowed by a single decisive strike, and there was no workable Plan B for forcing it to submit if it didn't. That's the key strategic failing. Persistent OWA threat is downstream from that.
The IRBMs are a huge problem. IRGC is using them sparingly, but they were not destroyed.
USAF has actually failed when it comes to 'scud hunt'. It doesn't have the combat ISR or strike capability it needs. As a result, the US basing and resupply situation is chaotic. The loss of the THAAD battery is extremely problematic, which is why they had to move one from SK.
The OWD capability allows Iran to attack tankers anywhere in the Gulf. Even with a surge in GCC state IAMD capability, ships cannot be protected. The failure to address this capability in planning was critical.
Obviously the DoD leadership is cowed by Hegseth and wouldn't give a true assessment, so we have a lions led by donkeys situation, but the operational plan was still bad.