Decent fun but I can’t help but feel that it could have been so much more. The big set pieces are mostly excellent and Denzel has a lot of fun with his role, however it never really justifies its existence.
The biggest issue is that the film repeatedly tells us what the stakes are and how we should feel, without showing us anything to truly back it up.
The emperors are bad - why? Based on what we’re shown, the main brother isn’t particularly cruel or unpleasant or incompetent.
Pedro Pascal’s General Acacius is a great noble man who wants the best for his people - does he? What is his grand vision? Why did he form his plan to overthrow the emperors? 
Paul Mescal’s Lucius is a slightly bizarre character. He’s probably miscast but he’s also not exactly given much to work with. He rarely speaks and when he does his accent is all over the place. I think Mescal works best with subtly and he never quite figures out how to tap into the supposed rage we are constantly told his character has. It’s a bit of a constipated performance, Mescal never really knows how far to dial it up or when to scale it back to something more precise. In his defence, the character is basically just a plot device to keep the story moving forward as opposed to an actual person. 
Denzel is given a much more straightforward role in Macrinus. He wants power and he’ll do anything to get it, and most importantly he’s going to have fun along the way. Crucially, he elevates the straight forward material in a way that Mescal and most of the rest of the cast struggle to. He’s a star with pure presence on screen. Russell Crowe had that in the original and Mescal just never gets there. In the final moments it’s most apparent, when the sight of Maximus’s hand flowing through the fields carries more emotional weight than Mescal’s semi-victorious soldier.