What i noticed and experienced is that while you got the best team by many bits, you shouldn't underesimate tactics and formations. You might be very offensive (you said you use 2 ST and 2 AM's) and with red arrows your STs teoretically become 4. If you also use a attacking mentality then you might be very unbalanced with your team disposition. Unbalances provides (in real soccer) lots of spaces between the 2 lines (defense-MId, mid-attack). That means that when facing narrow formations (4-1-2-1-2, 4-1-2-2-1, V styles) the players in the narrowed side are practically free in the loot of free space your unbalance creates.

Even if you are superior in quality, try to change your tactics and adapt to counter your opponent's ones. Leaving it to a superior firepower might backfire. Say i use 3-5-2 flat with 10 more Q, if the opponents counters me right and adds offside trap with fast defenders my firepower will be indeed lessened. But if i put an amc in play and negate the offside trap then the more Q my team has will undoubtely come out.
Try different formations adapting to your opponent's, i say.

Ofc, you might be doing this already and just totally be unlucky in league. gl :P

EDIT: if your league's teams are active, they might go full defensive against you due your superior quality. That's why it can become hard to score. If that's so, try a more defensive approach because you might be losing to counterattacks D: