What a coincidence, I just beat an opponent with 442 flat formation on an away match that is far better quality than mine. he has 6 of six stars player and even a 7 stars forward.
Click image for larger version.  Name: menang.jpg  Views: 142  Size: 95.1 KB  ID: 14924

on first half I use 4-1-4-1 which got me draw 2-2, on the second half I change to 4-1-3W-1-1 and got me two additional goals.

I use defensive mentality, down both flank, long passing, normal tackling and force counter attack.

So to answer your question, No, It's not unbeatable. Good luck man!