It's the topic of the first video. Gondor is strong, but the naval invasions are a huge pain to defend against.
I wasn't sure if things had been changed after the first video, but based on the first video I don't think naval invasions have been made any easier. While you've added new coastal settlements and made it a bit harder to move troops between them, you haven't made it any harder for Gondor to mount a naval defense.
The crux of the problem is that black ships are a 7/4/2, and dromunds are a 5/5/2. This means that while black ships have an advantage when attacking dromunds, they're at a disadvantage when attacked (while still costing 15% more). This means that Gondor can build a fleet in the sea zone just south of Dol Amroth / Western Belfalas. Any sea zone within 2 spaces of any Gondor territory is within 2 spaces of the Belfalas SZ. This means that Gondor can preemptively attack the Harad fleet no matter where they are before they have a chance to land. This is the same strategy I used in the current version. Gondor need only spend 24 IPCs a turn the first turn and any subsequent turn that Harad builds ships to completely neuter them.
Ideally the sea zones would be designed so that Gondor would have to split their fleet to properly defend against a Harad invasion, thus forcing them to spend more on defense than Harad spends on attack. One way to do this would be to give black ships an extra movement (but still make it require 4+ move to get from the City of Corsairs to the Gondor coast). Though this might make black ships too powerful. Another way would be giving black ships more defense, so they maintain their advantage over dromunds even when attacked.
Gondor still would have the money to outspend Harad on navy, but if Harad is more efficient than Gondor, it at least might make sense for them to try, And then Gondor will have to decide how much it can afford to divert from Mordor to protect its coast.