Various actors appearing in Gladiator II have been criticized for the accents they use on their characters, which are inherently inaccurate. Gladiator II is set 16 years after Russell Crowe's tragic revenge story of Maximus; Connie Nielsen returns as Lucilla, Paul Mescal plays her adult son and Pedro Pascal is the Roman general who is the new target of the protagonist's revenge. However, Denzel Washington has decidedly emerged as the best performer of the top six Gladiator II actors, playing the scheming Macrinus.
This is despite the controversy surrounding the Washington accent in Gladiator II. The actor decided to use his own New York accent, rejecting the choice of an African dialect for his character. Washington's reasoning for this was that there was no way of knowing what the historical situation was. Gladiator II figure would have actually sounded like, and he feared that his speech would be simply awful. However, Washington's response to this Gladiator 2 the critic points out some contradictions within the genre of historical fiction itself, which he only got around in his own way.
Denzel Washington rejected the use of an accent in Gladiator 2 - when none of the characters have historically correct accents
The rest of the Gladiator 2 cast uses British accents in Ancient Rome
Washington's line of questioning highlights the point that none of the other characters are British, even though that's how they sound in the movie. This is mainly because many major period pieces that take place in non-English settings tend to use British accents (such as Les Misérables). THE Gladiator 2 the characters also don't speak modern English, a language that doesn't even exist when the film is taking place.
For context, the Old English text Beowulf was written several centuries after the timeline of Gladiator II and is still incomprehensible to modern English speakers without extensive study of the language. The language spoken in the Roman Empire was Latin. None of these characters would speak English, none of them would sound British – both are creative choices made for the sake of marketing this film.
Gladiator 2's characters having different accents actually make sense (even if the accents are the wrong ones)
Gladiator 2 internal continuity with highlights kind of works
While the chosen accent doesn't necessarily have to be British, it makes world-building sense for some characters to have similar speech patterns. Lucilla and the emperors Geta (Joseph Quinn) and Caracalla (Fred Hechinger) all come from the same background of Roman nobility and probably look the same. Pedro Pascal's education of Acácio is less certain, but he also plausibly comes from an adjacent upper class and speaks similarly.
Paul Mescal struggles to maintain his British accent and adopts his true Irish accent in some scenes. While this inconsistency is a problem, it is plausible that he sounded like other characters. If Lucius had remained in Rome beyond childhood, he would have sounded more like his mother. In a historical context, he would not sound Irish, but he would sound like a member of Roman royalty whose speech is affected by elements of other languages due to his movement in Africa for years at a young age.
Macrinus would sound very different from the rest of the cast – his speech was probably consolidated as an adult before he was captured and brought to Rome – assuming they all speak the same language with accents that come from their native languages. For better or worse, Denzel Washington chose not to attempt the modern form of what would be his character's voice in Gladiator II. However, his New York accent really just asks for the same suspension of disbelief afforded to the other characters.