Trying to outkill the enemy without taking any flags will usually lead to a loss. You have to be really really dominant to have, for example, only one uncap flag, and defeat an enemy who has all the other flags, and all their CO resources and armour and cars and choppers etc.
To get the team to change, I'll try a combination of lecturing/hectoring combined with how I use the Commander assets. Biggest barrier here is what I have always considered a weakness in the BF2 game, namely the lack of a useful "chat" area. Our messages, even if we take the time to type them out, are displayed in the same portion of the screen as all other in-game messages, and can be quickly scolled off the screen by someone spamming "Yes sir yes sir" or "I need a medic here."
Anyway, try typing to the team and using VOIP to squad leaders. Tell them they will lose if they do not take some flags. And then use your Commander assets to support them. Instead of constantly dropping UAV and supplies in the area where that useless tank is spawn-killing, show them the empty flags with UAV. "Order" a squad to take a particular flag.
Joining the action and fighting, or taking the flags yourself, is as always your last resort. Commanders should not fight, unless it is to defend a base, or if it is 16-size map. However, if you fly into a rage and absolutely can't stand it anymore, and have to take a flag...take someone with you. If you go alone, good enemy Commander will spot you and arty you before you cap the flag.
If the team refuses to listen, in the dying minutes of the round, get on the chat board again and remind them of why they lost. Then try again in the next round. If they still don't listen, and still stand around the meatgrinder of the first flag, you might as well find another server. Either you are a bad Commander, or you just have a bad team that cannot be saved. It happens. Move on.
Oh, and I wouldn't use the 2nd option in the poll, dropping arty on your own troops. Just because people do not understand how to win is no reason to TK them.