A few rules of game play:
1. If you can destroy an enemy (or potential enemy) landing zone, base, unit, or territory with little or no risk, DO SO!
2. NEVER leave the enemy a safe have in the rear of your advance.
3. Protect your flanks as much as possible.
Sometimes an open, worthless, plot of land is perfectly acceptable.
For instance, why take Midway with Japan if you are storming the beaches of California on a regular basis? Odds are, American planes are NOT going to be attacking Midway or beyond at that point. And if America is not going to be wasting fighters and bombers landing them in Midway, then attacking the infantry there is a waste of Japanese resources.
Same is true for Solomons. If you are just raiding the Pacific with a few ships, why hit Solomons or even Wake? If your main flotilla is up in Alaska and the Irkutsk Peninsula (that's the dangly thing off the Eastern Sea Board of Russia, in case you were unaware) then hitting worthless islands are just a waste of time and resources.