Not really, no. The islands are necessary to carry out the bombings and the naval blockades. Taking the islands also prevented the Japanese using them to attack Allied supply lines. However, they did do this to some extent, bypassing bases like Truk and Rabaul that were too heavily fortified to take without heavy casualties.

Until the introduction of the B-36 in 1949, the USAAF didn't have a bomber with the range to hit Japan from any bases they had in 1942. To attack with what they had, the B-29, B-24 and B-17, they needed bases closer to Japan. Of the possible B-29 bases, the Marianas islands are furthest from Japan. But the simplest supply routes to them ran either through the Marshall and Gilbert Islands or past Wake Island. Both were Japanese-held. So one of these had to be secured, to prevent convoys being attacked. Taking these islands also allowed the US to base medium-range aircraft on them to support attacks on the Marianas. Once they had taken the Marianas, taking Iwo Jima and Okinawa allowed fighter aircraft to escort the bombers, lowering casualties. Shorter-ranged bombers could be based from these islands. Iwo Jima also provided a recovery airstrip for damaged bombers. The decision to take the Philippines followed a similar rationale - the main Japanese resource areas are in Indonesia, and the main sea lane between Japan and Indonesia runs through the South China Sea. By taking the Philippines, this can be closed effectively. To take the Philippines, you need to take the Palau Islands, and some of the Dutch East Indies.

On a smaller scale, taking bases like Guadalcanal allowed the US to cut off the larger Japanese bases. Once Guadalcanal fell, aircraft from there could support landings along the Solomon Islands chain. Airbases on these islands could then be used to cut the supply lines to the major fleet base at Rabaul, which was too strong to capture. The Japanese bases at Truk and Babeldoab were similarly bypassed by the Allied advance, before being neutralised by Allied airpower from the bases occupied.

While the US Navy could operate in close proximity to Japan without needing to take islands, as they did to launch the Doolittle Raid, this would have been very dangerous to do as a long term strategy. The Japanese island bases formed an effective defensive parameter - they operated highly trained anti-shipping air units from these bases. While these took heavy casualties operating against carrier-supported forces, their losses would be more easily replaceable than aircraft losses aboard a carrier. The carrier would run out of fighters before the IJAAF and IJN ran out of bombers. Any ship that took major damage inside the perimeter would be lost - the experience of the Mikuma and Mogami at Midway is instructive to the chances of survival of a crippled ship against air attacks. A damaged ship would have to cross over a thousand miles of ocean, much of which would have been within range of Japanese airbases. Ships operating at long distances from their bases also tend to have limited time on station - they would have spent much of their fuel in transit. The same holds true for submarines, which while generally protected from Japanese air attacks, spent long periods in transit. Islands needed to be captured to provide rearmament, refuelling and repair positions.

Finally, taking islands prevented the Japanese from operating from them, and interdicting Allied supply lines. This was the rationale for attacking the Solomon Islands. Had the Japanese finished constructing their airbase on Guadalcanal, they could have attacked Allied convoys to Australia. It could also have been used as a staging base for an attack on Fiji or Samoa, both of which could have closed the sea lanes to Australia. While these moves could have been defended against, the resources which would have been needed to do so were just as high, if not higher as those needed to take the Solomon Islands.

Islands generally have several advantages over ships - they can launch larger aircraft, are generally unsinkable, and provide useful bases for shipping. While Guadalcanal was mostly used for tactical aircraft that could have been carrier launched, there was, and still is, no ship afloat that could compare to Tinian, Guam or Saipan as airbases.