I find ancient naval warfare interesting and had high hopes for Mare Nostrum. However, I have found Mare Nostrum disappointing both as simulation and a game.
Most fundamental problem is the WEGO system. Given the high movement rates in the game, it makes contact with the enemy a matter of luck. In addition, even if you gain an advantageous position to the your foe's rear, you don't have a good chance of exploiting it. The movement should have been slower (as in the board game Trireme) or IGOUGO with reactions (as in the board game War Galley) or there needed to be rules for tailing a foe (as in most air warfare games).
Another major problem is the ease of bow rams (or oar rakes). It is an effective tactic in this game, but was rarely performed in history. There is only 1 mention in ancient history of trying to deliberately smash an opponents oars (in Diodorus's account of the Battle of Chios). This rare tactic should not be the most common and effective tactic in the game. Not only is is ahistorical but charging straight at your for is less interesting.
The actual tactics of ancient warfare have no place in the game. No one playing Mare Nostrum would attempt a Diekplus (passing through the enemy line and then turning and ramming) or a Periplus (outflanking the enemy and ramming from the rear). There is no benefit to forming a double line (to catch the enemy ships when they turn to ram).
The command control rules are insufficient. Formation orders are only a convenience, you are expected to plot an order for every ship. Do galleys carry radios? Are drones giving every captain a birds-eye view of the battlefield?
These ships when under a skilled crew, were incredibly mobile. A trireme could make a 180 degree turn in a ship length at cruising speed. That, rather than arbitrary modifiers should be the advantage of a good crew.
There are some purely game problems as well. It would good if you could put squadrons under computer control, so you could focus on commanding 1 squadron, making large battles easier. The game also lacks a true scenario & ship builder.
I can only hope that someone tries doing an ancient naval game better.