Activity does matter in chess and when it comes to semi open games you need to pay attention to the open file to help the activity of your rooks. If your rooks can control that file, most of the time the position will favour you. But controlling the open file is not enough; you must also stop your opponent from neutralizing its effect, create some targets on it and ideally some penetration squares.
Anatoly Karpov against Boris Spassky, 1974
Q: In the position above, Spassky’s last move was …Be7 threatening to play …Rd8 after which White wouldn’t have any serious advantage. How can he stop Black?
A: Karpov did it as follows:
Almost forced as if …Nb8 then the rook on a8 is shut in.
2. Rxd8!! Bxd8
If 2…Rxd8 then 3 .Nxe5 is followed by penetration via f7 square. Though it’s worth considering 3…Qc7, a good calculation exercise.
Followed by Be7, so Spassky resigned.
The following instructive game of Peter Svidler was played in 2007 against Shakhriyar Mamedyarov, and provides a great illustration of our theme. After Mamedyarov’s 18 . e4 and 19 Re1?! he was never in the game: