I am not sure what you mean by currently not entering ocean is a promotion. Surely it is the opposite. I think there are various options to look at:
Firstly bring back Frigates to Astronomy when units can embark across the Oceans. I don't like this too much as it brings them close to Galleas.
Secondly, bring back Galleas to an earlier tech, as it seems strange to be able to obtain this at the same time as Caravals. Whilst Galleas are upgraded Droman, Caravals are not only upgraded Trimeres but have a massive promotion to cross oceans. This obviously will not sort the problem of Galleas crossing oceans but does balance the naval units better.
Thirdly, push back Galleas & bring in unit between them & Frigates that can cross oceans but lot perhaps still weak unit. This is unlikely, as developers reluctant to add additional unit types.
Fourthly, & my preffered option is to enable embarked units to cross oceans when Navigation is introduced, at the same time as Corvettes & Frigates.
I think that something needs to be done though as it is a bit silly when your armies of Pikeman & Knights (including any non military unit) can parade around the world in flimsy craft, your top range naval unit can't.