Ok so iridensys ur opponent plays 4-2-3-1 formation.
So basically in 4-2-3-1 there is a lack of a DMC to counter AMC.hence using an AMC in ur formation can do tphalf the job of countering the opposition.
Secondly,in CENTRAL midfield,he only has two players.if u choose a formation that is strong in midfield u can easily win the game.
Thirdly,his full backs are completely exposed to your wingers as in opposition team there is no ML/R.
And finally,he has three attacking midfielders in his team.this is good and bad at the same time.good because his players can't track back during counterattack sand bad because he can troll ur fullbacks.in ur formation it is necessary to play DMC to counter his AMC

Basically use a formation like 4-1-4-1 or 4-5-1v which gives you freedom to play thru middle or down flanks and which enables u to play counter attacking football and obviously one which has DMC to counter his AMC