So no one saw Euron coming!

Yea, I didn't care for it especially since Yara was this master captain and it seems unlikely they wouldn't be able to spot the threat from a long ways away.

They've been giving advance warning for at least a year that they want to wrap this show, so I was prepared for stuff like this to happen. What we are seeing now was planned out a long time ago. They knew they wanted 7 seasons, but along the way realized it wasn't enough to tell the story, so they added 3 more episodes. And some stuff still had to be cut. I think most of the people involved care very much about the show, but it can only go so long before actors, writers, producers start to burn out and need to move on to new things. Knowing there is an end helps with that a lot. Especially a high profile show like this, where the lead actors are constantly getting movie offers and producers get a blank check to make whatever they want for their next project.

That hardly matters since they know he was pledged to kill them

I'd have to question if Euron was a more experienced seaman actually. You're probably right, I don't really follow GOT that much, but Yara was commanding, sailing and working her whole life with a large fleet ... but Euron may have been sailing, but where was he commanding or really getting experience. Yara broke in to get Theon out ... now, that was a seasoned commander, strategist, leader ... who Euron sneaks into the castle and kills his father? Without a clear backstory it seems almost goofy to me, not to mention that they could build a fleet like that in what was basically overnight. That's why to me this season seems to be rushing and not the normal careful story quality of other seasons.

That doesn't mean he can see in the dark.

Honestly, I don't know if I wasn't paying attention, or it was the way the whole battle was edited, but it looked to me like it was just that one big ship. But I guess there was a fleet out there somewhere firing those fire thingies.

Kind of hard to miss those enormous ships of Euron's even in the dark - there should have been several watchmen set just as a matter of good practice. Even if they didn't expect to meet anyone there could also be other dangers that might crop up at sea. Kind of unbelievable to be taken like that with an attack before Euron's fleet is sighted right off their bows.

GOT has a problem with continuation, Euron's fleet being built overnight is a good example. Another example is Littlefinger traveling to all parts of Westeros too quickly while other characters need a considerable amount of time for the same voyage. But the most damning example is Varys being in Dorne in one scene, and with Dany in Essos in the next scene of the same episode in season 6.

Maybe Euron sneaking undetected with his ships is a part of the same problem. Maybe in reality Euron attacked Yara's navy with fireballs, then an hour or so passed while he caught up with her navy, and then he boarded her ships. But the show creators were skipping scenes to get to the point, and that's why we have impression that he came out of nowhere.

The stupid thing about Euron's fleet is that it was constructed literally overnight when he ordered his people to cut down every tree on Pyke...yeah, that's not enough trees for a fleet like that or a ship of that size, buddy.