It's a tactic's game. It's not a flaw if it's not realistic from that point of view. If we use every game a 4-4-2 formation and win it all, where's the charm? I was very frustrated too at the begining but than I realised that FM07 is way better than 06. I'm Ado Den Haag now and i use differnt formations and tactics depending on the other team. I watch them carrefully in their last matches, i real all the reports from the scouts and than I choose what to do. For example, against Alkmaar, a team that uses a strange formation, I've chosen two AMRLC on the wings who can swith places at anytime. That's because they didn't have winger. Passing down both flanks, etc, etc, etc. Anyway, my opinion is that every tactic should be made only after you know very well each player. Ex. fullbacks don't have pace and acceleration, keep them low, if a DMC has great long shots and good tackling and average speed, let him run forward and shoot from distance, etc, etc. If the target man has good heading, give him passes to the head, if he has great pace put him to run onto ball and many, many, many more. In reality, Ferguson (because you've mentioned Man UTD) knows everything about his players, even what they eat and that's realistic. If he plays every game 4-4-2 formation, that doesn't mean that he uses the same tactic. Believe me, he barely uses same tactic twice in a season.
P.S. I've spent more than 2 days (aprox. 15 hours) to watch friendlies and know my players very well. Than I've started the season. With the most tipped team to be relegated, I'm now 4th after the half of the season. I know, i play really defensive, I score controversial goals, I don't make a show in my games but I win, or draw. The proof: Won with Ajax and Feyenoord (on their territory), had great draws away with Groningen, Alkmaar but also lost home with Willem II and Hereenveeen.Anyway, I only have 3 losses and all I know now is that I want to catch up Uefa Cup. I know it might be impossible but that's a living proof that tactics DO work, if you use the right ones (not the real ones).