This episode’s ending is 100% a show invention so that people don’t complain about too many gay characters being killed. In the book Laenor absolutely dies.
And I agree, Laenor is complete garbage. Honestly, this makes Rhaenyra and Daemon look even worse than if they’d just killed Laenor, because not only did they kill a totally innocent person in his place, but they put Laenor’s parents through all this grief for no reason (and there’s no way they know the truth; I very much doubt Corlys would be ok with his son and heir just fucking off to Essos).
I’ve seen some theories that Laenor may come back later when his family needs additional dragon riders, but him being revealed as alive to Westeros would mean that Daemon and Rhaenyra’s marriage is invalid, and her children with Daemon would be bastards. It’s of course possible that we never see Laenor again, and he is truly ‘dead’ for all intents and purposes. But that has issues as well: not only does it turn Laenor into an absolute bastard, but it also means his dragon Seasmoke would be left without a rider. Dragons can only be bound to one rider, and in the book Seasmoke gets claimed by another character eventually.
As good as the episode was overall, the ending definitely left a bad taste in my mouth (though I guess that’s only because I know what happened in the book, and what will happen in the future).