@Buchan is probably right about him suffering more because of how we play now (even if he overstates the hoof ball stuff).
In 17/18 he scored 27 goals with 17 assists in all competitions which is a phenomenal output.
Then in 18/19 Klopp started to focus our creativity through the full backs. Firmino’s numbers dropped to 16 goals and 8 assists. Klopp’s switch to more direct football is probably due to how we struggled earlier on in his time at Liverpool against deep defensive set ups (similar to how Burnley played yesterday). Teams squeeze the pitch and stay deep/compact giving Mane & Salah no room to operate. Having the option to play balls over the top can open up the space for Mane & Salah to run onto. Most full backs aren’t as fast as either of them either but I think we focus that tactic more on our right than we do on the left.
Firmino suffers with this because he doesn’t have the pace to run in behind, so he comes deeper for the ball and also to try and open space by pulling an opponent out with him. He’s become a fourth midfielder now and his numbers have suffered as a result. It’d be interesting to see a heat map of where his shots are from. They’re probably not in statistically ‘good’ places to have a shot on goal, although he’s missed some sitters this season.
I think it’s also about adding an additional body to the midfield to give us a numerical advantage there. For comparison, Guardiola normally plays a front three but instead of Aguero or Jesus dropping, he’ll push someone like Walker into midfield to make up the numbers instead.
Even though his numbers (and sometimes performances) this season don’t necessarily indicate it, we’re a better side with him there than we are when he’s not.