I think there is nothing wrong with using others' tactics. First, there is no guarantee one will work for your specific team. Second, as socks said, nobody has found the one and perfect. Finally, you are not competing with people (unless you do

), but with AI. Using common knowledge is totally fine.
On the other hand, I think by using a tactic you did not created, you miss a lot of fun. Yes, it is not easy to build one in FM07, and you get frustrated when a tactic does not work, but once you succeed, it is great feeling!
As for the rafa's comment, that's one more reason to read these forums to pick up ideas, re-think and re-work them with own judgement, and play.
Good luck :thup: