This season Firmino played as a midfielder with Mane and Salah taking up the striking position the vast majority of the time:
Lacazette: 49 apps, 19 goals, 13 assists
Firmino: 48 apps, 16 goals, 8 assists
Last season Firmino played as the 9 (though was still not the primary goal scorer or focal point, and again Salah much more advanced):
Lacazette: 39 apps, 17 goals, 5 assists
Firmino: 54 apps, 27 goals, 17 assists
Over the last two seasons then:
Lacazette: 88 apps, 36 goals, 18 assists
Firmino: 102 apps, 43 goals, 25 assists
All this while not even being the primary, or secondary goal scoring option and contributing way more off the ball. But I already know you're not to be convinced there.
Luckily Klopp has one as one of his most important players in an historically good Liverpool team that just won the CL. Lacazette is a pretty good player though, he just isn't on Firmino's level.