What does this have to do with anything, mate? If you want to have a semi-reasonable discussion, you'd do well to argue in a reasoned way - as opposed to making accusatory and inane 'Really. Well well" remarks that add nothing to the discussion. Some of these teams are stronger in
certain positions, according to me anyway - center forward is one of them, according to me. And yes, Firmino. Really. He is very versatile, selfless, defensively capable in a front-to-back approach - an all-round industrious forward with better spatial awareness and more intuitive movement, again according to me - definitely the type of attacker that would thrive with both Sánchez and Martial in a withdrawn role in a dynamic forward trident. Plus, since many find it hard to look beyond raw, superficial stats when comparing players (because pure production data doesn't account for the myriad complexities) - he has 17 goals and 8 assists in roughly 2375 minutes in the League and European competitions vs. 16 goals and 5 assists in roughly 2675 minutes in the League and European competitions for Lukaku with better secondary attacking stats (needs a minor update).
So there you go. Mind, stats can be poor representation of players
in isolation - just to reiterate a previous point, and I don't think José has appreciation for players of Firmino's ilk - so it's an unproductive exercise all things considered, as he would never opt for Firmino over Lukaku because the latter is used in a more conventional striker role. Then again, the OP proposes - “straight swap would you”, so I was just giving my personal opinion.