What he means is that human players will A. bring much more powerful forces against you and B. will see in advanced that you are spamming carriers and thus build lots of flak and light frigates and possibly capital ships with anti strike craft abilities. Not to say that such a strategy can't work, and in fact I think carriers are among the more difficult ships to counter, as they can produce either fighters or bombers, which are countered by different ships, but it will be much harder to do on human players.

As to a fighter/bomber ratio, it used to be that you need to have air supremecy with fighters, but that doesn't seem to be true anymore, especially if you have flaks with your bombers. Ultimately it depends on what your opponent has. If he has a lot of strikecraft/LRMs/Light frigates, go fighters. If his main strength is capital ships, heavy cruisers, or if he has plenty of flak support, go bombers.