Except you most certainly can hit them with a destroyer. Or did you forget? https://www.rt.com/news/322881-russia-cruise-missiles-isis/
But cruise missiles do not have nearly the same precision as air support fighters.
An F18 flying over your infantry (or infantry of allied partners) will respond near instantly to a call for assistance. In contrast, that cruise missile may take several minutes before it reaches the target.
Nimitz, Eisenhower, Vinson, Roosevelt, Lincoln, Washington, Stennis, Truman, Reagan, and Bush make 10, with Ford entering commission later this year to make 11.
In any case, the US doesn't really have that many carriers. I mean, we have more than the rest of the world. But they're so bloody useful..
If you count things in the class of what the US calls carriers, the rest of the world has, I believe, 0 (some sources refer to these as "large-deck" carriers.)
If you want to include what the rest of the world has for carriers, you need to go to "medium-deck" carriers, where the US has more (even without counting the large-deck ships) than the rest of the world combined in the form of its amphibious assault ships (LHA/LHD).
But with only Helicopters and V/STOL aircraft... the Supercarrier is actually a better system. Helicopters don't provide the straight immunity or take advantage of modern asymetric warfare: Helicopters can be shot down by enemy rockets.
V/STOL aircraft like the Harrier Jet or F35B are expensive (either in lives: due to the high number of accidents on the Harrier, or costly in specs. IIRC, the F35B doesn't have the same specs as the other fighters). The Supercarrier filled with F18s might be cheaper than an Amphibious Assault Ship filled with V/STOL aircraft.
So from an overall cost perspective, Supercarriers with standard aircraft still remain the best bang for their buck.
The "Carrier Strike Group" is simply all of the other ships (destroyers, cruisers, etc. etc.) that follow the carrier around.
The Strike Groups will remain without a Carrier. They basically are the US Navy, aside from the subs we have hidden around the world.
Furthermore, all of the other ships are completely useless in Iraq, Syria, and Afghanistan. You can't hit ISIS with a Destroyer. You hit them with Airplanes, carried over by Carriers.
The firepower of a single US Carrier is bigger than the vast majority of land-bases in the world. A US Carrier can also move however. Its probably one of the most potent weapons of the US.
Basically, we have ten moving naval bases, that can be stationed anywhere in the ocean. Each one can go toe-to-toe with the vast, vast majority of land-bases in a particular region and win.
Or we can build another few $500 Million to $5 Billion bases in Afghanistan that we later abandon when we change administrations (Bush had different plans than Obama).
The Carriers are a far better use of money than building actual bases. Despite their high costs.