Rome failed when it ceased to be a Republic.
The Roman Kingdom started in 753 BC and ended in 509 BC, the “Republic” dated from 509 BC to 27 BC, the “Empire” dated to AD 476 and then morphed into the Byzantine Empire that lasted until 1453 AD.
The “Republic” was an Oligarchic Timocracy. Certainly NOTHING that we would want. Moreover, the post “Republican” Roman Empire lasted over 900 years after Ceaser replaced the structure of the Oligarchy with a new structure, but still Oligarchic just less Timocratic.