That's a bit of a simplistic way to look at it. First, Salah has just matched his goal output from the two previous seasons, and he's done better than 18/19 and 19/20. Second, Firmino was also a 1 goal in 3 player for Liverpool, but did a lot more than that - Gakpo could be similar. Third, Gakpo and Nunez numbers are a bit skewed by only being measured in a crap season for Liverpool.
I do agree that their forward line is not at the level of when Mane, Salah and Firmino were all together and at their best, but it's still good enough to get back to comfortably get back to top four, if they sort out the midfield.