The main issue was that the Allies had almost complete air superiority, as well as a few innovations to anti-aircraft fire, such as delayed, proximity fused shells, that made attacking an Allied carrier group extremely difficult. In addition, most of the Japanese pilots at the time, aside from a small elite cadre being sequestered, completely green.

In order for a plane to attack an enemy ship with torpedoes, the plane will need to be flying relatively close to the surface. This makes the planes hideously vulnerable to anti-aircraft fire, as they will be travelling in virtually a straight line at a low angle to the surface, meaning anti-air emplacements would have an easy time shooting at them. In addition, they were vulnerable to aircraft in the battle group's combat air patrol, which would be able to use the sun to hide their presence from the bombers until it was too late.

For naval dive-bombers, their main issue was that while they were relatively safe from flak cannon fire due to their high altitude and sharp dive angle, in order for them to attack properly they needed protection against enemy fighters whom would almost certainly be on them to frustrate their attacks. And green pilots were basically food for the now-veteran Allied fighter pilots, thus making it extremely unlikely that the dive bombers would ever get into position for an attack run.

The advantage of the kamikaze was that it didn't matter if the plane was damaged-while a plane that attacks from the surface will likely fall into the sea and a dive bomber that is shot down will spiral out of control away from the ships, a kamikaze is already coming in at a collision angle. Even if the pilot loses control, the plane basically acts like a missile. And it required relatively little training to do so-flying your plane from point a to point b is a relatively simple procedure, especially when compared to dogfighting, takeoff and landing, carrier operations, and so forth.

A plane, full of fuel, ammunition, and a bomb, will do a lot more damage when it slams into an enemy ship than just a bomb alone.

Also, hitting ships from the air in WWII was not as easy as it sounds. These munitions were not guided (well, the Germans used some guided bombs but that's separate from the Pacific Theatre) and misses were very, very common. I'm currently reading Japanese Destroyer Captain, which is a memoir by Captain Hara Tameichi of the Imperial Japanese Navy. Hara goes over several engagements in which he partook in, and one common trend in these engagements is ships frequently managing to survive aerial attacks due to the enemy simply missing. This seems to have been particularly true when facing less experienced Allied pilots early on in the war, and considering that Japanese pilots during the latter part of the war in the Pacific often suffered from a serious dearth of both training and battle experience, I'd imagine that they were even less effective at standard bombing or torpedo runs. Even experienced and trained pilots often missed their targets. An example of this would be the Battle of Cape Engano, which was a part of the larger Battle of Leyte Gulf. At Engano, what was basically a diversionary Japanese fleet faced off against a much, much more powerful American force and lost pretty badly. The Japanese lost air superiority pretty quickly, meaning that American pilots were free to attack Japanese ships with the only opposition coming from anti-aircraft fire. These pilots did a pretty good job of it, sinking all four of the Japanese carriers. However, the Japanese battleships Hyūga and Ise survived, as did most of the Japanese cruisers and destroyers, largely due to the virtue of them not suffering that many direct hits. Sinking as many ships as the Americans did at Cape Engano required 527 sorties, and remember, the Americans enjoyed complete air superiority over the Japanese. This goes to show the difficulty required in sinking ships in WWII by standard bombing or torpedo runs.

By the point in the war Japan started using kamikaze tactics, they had a serious dearth of well-trained airmen and could not expect to enjoy air superiority in almost any engagement they had against the Americans. It is also worth noting that American naval AA guns were superior to those the Japanese possessed for the entirety of the war in the pacific. Based on all these factors, using kamikaze tactics makes a lot more sense.

I typed out a full answer but I deleted it because the other two answers here already cover 2/3 of it: kamikaze tactics were much easier, and Allied task forces by 1944 were so overwhelmingly well-defended that attacking them with what the Japanese had was akin to suicide anyway.

I do want to mention one other point, however: by not having to return to base after the strike, the effective range of an aircraft is doubled, or alternatively it can carry a much heavier load to the same distance.

Edit: However, I should clarify that while some missions, like the raid on Ulithi, were conducted in this way, not all kamikaze missions were. Pilots were instructed to return to base when possible if they could not find a target, and kamikaze raids ideally would have pathfinders and escorts accompanying them, which needed to be within their normal combat radius.

My Father was WWII Pacific sailor and was off Okinawa and several other battles. He operated one of the little landing crafts and 40MM anti-aircraft gun. He told me really the only thing that scared him was the Kamikazes because if a plane dropped a bomb there was a good chance it would miss and the plane would fly away. Those dropping bombs also tried to avoid the flack and made it more difficult to accurately drop the bomb. But the Kamikazes just kept coming. Of course many were not very experienced pilots and not familiar a lot of the time on how to avoid the AA and would fly through it.