Why the 343 formation cannot be effective
Teams who play it cannot dominate the midfield because they have a pivot of 2 players, 2 number 10s, resulting in positional play and when defending they use the 5 defenders (2 wingbacks included) and the number 10s have to drop back into midfield positions to help defend, meaning there is no consitent press, striker isolated.
It requires team to play positional football. basketball football, where the ball is moved from player to player, with these players only doing any switches to create traingles or make runs from midfield when there is a lot of space, when there is no space the formation rarely sees any movements.
The formation does work against passive managers but it is quickly found out when a manager tries something different against it.
Roma has regressed ever since they changed from Ranieri's 352 to Gasperini's 343, we saw what happened with Ruben Amorin's 343 with a pressing pivot ignoring football basics of using a DM, Dortmund has looked very ineffective, a better squad but rarerly dominating, Alonso quickly learnt that it would not work at Real Madrid, Lens despite having the second best squad in Ligue 1 have struggled recently vs weaker teams. Conte's napoli did very well with the 451, they are much worse this season after moving back to the 343.
It is also indictiment on those who appoint football managers. Teams have to look at managers who have done it at youth level, smaller leagues and allow them to express their ideas. The rotation of the same managers is making football extremly boring.