That would be the ideal case, but people, mostly when they are in the beginning of the game, are not able to accurately measure their own strength or others. In my opinion, we as experienced players should give advise to them, and explain why they should go for a specific target. I have saw people saying that their mirror is very easy, I think they could take if the play the right way, and as such I assign the target to them and give the guidelines and the warning they should pay attention at. For example I tell them to watch out for the donated troops in city center, to take out a specific building, etc... In the end most of the time they rush to city center to get the quick victory, don't apply sabotage a howitzer comes from the city center and boooooommmmm... Attack, lost and people say " I don't know what happened", and I say " I told you to watch the city center and apply sabotage,but you let the howitzer come out and boooommmm! Go watch the replay.". And they go and they tell, "You were right, I should have done better.".
The problem with inexperienced player taking a target from their choice, is because they aren't yet familiarized with all the game elements and mechanics. In my opinion, you only get the real grasp and feel of the game when you enter the industrial age - which is the age I am at. There you start to deal with a lot of different thing, like planes, a loot of more troops, taking out sniper towers, bunkers, anti-air guns, etc... Everything changes from the simple combinations of troops from the lower ages, because you have limited choices. In the industrial you have to take a lot into consideration - and even more in the global upwards with the silo, which I am about to experience. But because of all of this, you become better, so I think the industrial age is an age where you should spend your time in, and to learn the game mechanics. I stayed in there for the last 6 months, I don't regret a single day there - I am almost maxed out. Until there you should have patience and coach the new members, and hope they stick with the game long enough to be valuable members. From what I have seen most people that reach late industrial or early/rush global are those that didn't take the time to learn the game mechanics, and that point they take a hard time trying to learn and getting rid of old bad habits.
Another topic that would interesting to discuss would be, "Is it worth the effort to coach newly arrived members to the game? Or just those that have already some month in game?" I ask this myself everyday, because we have members that join after a week of game playing, have rushed to medieval age gunpowder, we advise them to take their time and mature at their current age, or it will be worst with every age rush, and when they understand the commitment they have to do, they leave the game... With that you sent a almost a month of coaching someone that really didn't have will to play the game. Then a new member comes in and you start all over. This sometimes makes you frustrated, but I think it makes part of the coaching. Sometimes you to coach 10 to take out 2 good players... I tend to think "Ok, it is like a team of football kids. Not all of them will be professional players, but 1 or 2 can be. Despite that you have to training all of them. Inhale... Exhale... Inhale... Exhale... Ok, let's do it!"