You'd prefer Barca having to find Lautaro a new club and burn another 100m to find a replacement in a few years?
Unless Lautaro proves he can be a high volume goalscorer which Aguero was at his age then he should not be signed. Might end up being another Gabriel Jesus with all the intangibles in place, but not the most important part: Scoring goals.
Reason I mention Aguero is because that's the player he's always compared to, and Aguero at the same age or actually younger proved to be a different beast at Atletico.
Lautaro has apparently extended his contract with Inter so that option appears to finally be closed but yes, I would prefer a profile of Martinez to Haaland for Barca despite, yes, knowing Haaland will mark an era as a goalscorer.
I prefer the fit of Lautaro, the Kun comparisons are predictable & pointless - they are two different players. There's not even a certainty Lautaro will reach world class level but I see qualities in him that few other strikers offer and could both help Barca & Argentina for the next WC would him & Leo have time to develop chemistry
Plus, the physical realities of a profile of a striker like Haaland is that they cannot count on speed/acceleration for very long at their size - it's the first part of their game to rapidly decline. Then, tall strikers often have chronic back issues and will ultimately rely on their technique & strength to be factors - that pressing ability will fade
I won't even enter into the Raiola factor whereby no reason to believe his client will be staying at his next club for very long before negotiating another lucrative megadeal. If this were for a Messi-heir playmaker, I'd support it - for a CR like striker? Never. You can forget building a team from that approach much less with the style of Barca
A pressing & mobile forward is what Barca require who can find the back of the net with clinical ease so it doesn't have to be Lautaro either. If we go all in for a signing, it should be for a decade of dominance else and I don't see a player like that in the market