Yeah, but Midway had 10 guns and Iwo had bunches of them also if one adds the ships from the accompanying fleets at Midway the Japanese had just about as many ships at Midway as the US did at Iwo. Also, it does not appear that the guns at Midway were enclosed in concrete (at least the pictures I have seen).
Again taken from this:
https://www.wargamer.com/articles/what-if-invasion-of-midway/
While the Japanese were indeed going to subject Midway to a preparatory naval bombardment prior to the invasion, only the four heavy cruisers (Suzuya, Kumano, Mikuma and Mogami) and supporting destroyers of Cruiser Division Seven were tasked to carry this out. Using their battleships to conduct naval shore bombardments went against official Japanese Navy Doctrine at the time, and would continue to be so until the Battle of Guadalcanal, a few months later. Even then we must not overemphasize the effect of Japanese battleship gunfire upon fixed land targets. In one night off Guadalcanal a few months later, the Japanese Battle cruisers Haruna and Kongo fired over 970 14" high explosive, incendiary rounds into Henderson Field, and the US Marine Perimeter, and were unable to knock out the US "Cactus Air Force" there. The following day the Marines were, somehow, able to put aircraft aloft to bomb and strafe the Japanese transports that had deliberately been run aground several miles down the shoreline from the Marine Perimeter.
That is also my reading of Japanese dispositions. The BBs and their associated CAs and DDs were loaded for bear (AP, USN fleets), not for playing whack-a-mole (HE, Wake). The Japanese were notorious for producing overly intricate plans, rigidly adhered to those and those depended upon everything going just right and proving often quite disastrous when one step failed. The initial Dec '41 series of attacks nearly got badly derailed by the initial repulse at Wake and delays imposed at Bataan. As it was the Japanese had to switch forces back and forth between Bataan and Malaya, they simply did not plan for nor have the forces to allow for any delays. Overall they got exceeding lucky in their initial SE Asia offensives. So I totally agree with the author of the above that the Japanese were not mentally flexible enough to quickly switch forces to reinforce their bombardment ships.
That leaves 4 Mogami class CAs with 40 8" and 32 5" dual purpose of 7th Cruiser Division and 2 DDs with 12 5" dual purpose guns of 8th Destroyer Division. I don't know what the 4 minesweepers and 3 sub-chasers of the Minesweeper Group had, but 4"/100mm would be about their limit. Throw in the Escort Force with 10 DD of the 15th, 16th and 18th Destroyer divisions and a command CL (Jinsu) giving 60 5" and 7 5.5"/140mm. That's a total of 40 x 8", 7 x 5.5" and 104 x 5" guns. That sounds nice, but of those front line 17 combat ships, 4 have 4" belt, 1 with 2.5" belt and 12 with no armour.
You still have to spot the shore guns. Put up spotters and fly then anywhere near Ford or Sand Island and they are flying into 24 x 3", 8 x 37mm and 18 x 20mm AA guns as well as 40 x .5" MG, a right nasty, concentrated little FlaK nest. They had lost 11 aircraft with another 14 heavily damaged in the 108 plane Wake air raid, so I would guess that a dozen or less spotter aircraft that would have to loiter around Wake would have have some very, very interesting times. Even then, did Japanese DDs have the training to cooperate with spotter aircraft like their BB/CA bigger brothers? I suspect not enough to be effective, if any.
If the Japanese approached at night, like at Wake, then, like at Wake, the USMC gunners still can hit but be quadruply difficult to spotted and be hit by the Japanese.
My guess for that action is the Japanese approach and promptly loose a CA and a DD. By the time they realise the opposition and draw off to a safer distance they loose another DD or two and have another CA badly damaged along with a couple of DDs, with a good chance they don't make it back home. By then the Japanese have only 2 CAs, a CL and 7-8 DDs still in the fight and at a distance where anti-shore accuracy is very badly degraded.
If they are still stupid enough to try to force an invasion then the have the same problem the US had at Tarawa, being hung up on the coral reefs but with only rubber boats instead of amtracks to cross those reefs and being outnumbered by the defending troops. It would have been an utter, utter disaster.