Speaking Etruscan does not change any of the 'necessity' factors pushing Rome to become a military powerhouse.
Being first, the Etruscans were more complacent than the Romans. Their fate wasn't dependent on a single city. The Romans had the fear of their city being taken. That fear drove them. In contrast, the Etruscans were in a more comfortable position. The rise of the Romans took the Etruscans by surprise, and by then it was too late.
Indeed, the Romans never felt secure. In contrast, the Etruscans remained blissful and stable for centuries. They were the status quo. During the relevant time period, Etruscans never had to struggle for their survival the way the Romans did. The Villanovans were a distant memory. Suffice to say, the Etruscans did not have the same imperative for expansion as did their Italian neighbors. That's not to say they wouldn't expand at all under the right conditions, just not at the rate of the Roman otl.
Maybe the rest of the Etruscan world is devastated by civil war or Gaulish invasion and Rome emerges dominant.
The Carthaginians and Greeks are motivating factors for strong central authority. Although, in the otl, they largely butted heads with Rome as a response to its rapid expansion. If it takes longer for there to be a unified Italy, then Carthage and the Greeks are more likely to turn on each other. The Gauls remain relevant, but the Etruscans should be able to handle them. Arguably, a unified Gaul (at least a large warband) was a response to a unified Italy.