Even Arsenal is struggle to beat Fulham in home, they really need Saka, he only play for 7 minutes and can score a goal.
Arsenal ain't a good club without Saka. It's because he is the only player they can rely with. They can play well when he was there, but when he's out, they're clueless about what to do. He's the reason why they're getting very optimistic to fight against Madrid.
I see no better player in Arsenal than him. he's the only one who carried them, and it happens very often.
Basically Arsenal played without strikers and of course Arsenal lost some points when Arteta put newcomers or midfielders like Trossard, Edegaard and Merino in attack.
In addition, Saka is a great striker in his own right who can create a dangerous moment and score a goal, but before he returned to the lineup Arsenal beat PSV 7-1 and Manchester City 5-1, so of course Saka's return helped Arsenal a lot, but was certainly not decisive.