The lack of marriages in later GoT seasons is insane
To compare the books to show how peculiar marriages (to form and/or strengthen alliances) are to politics: Book!Daenerys is flooded with proposals and suitors since every man (no matter status or age) believes TMoD should be his wife, make him king, and give him "many strong sons." book!Rhaenyra was the crown princess of House Targaryen at its peak of power and had already promised Laenor Velaryon, yet she was proposed to by all kinds of men. Even by Forrest Frey. A man who was not even the firstborn son and who came from a house way too minor to be even considered!
To mention only a few plots and alliances, that have been/are built upon marriages: Catelyn and Brandon/Eddard, Alys and Signor, Maegaery & (Robert)/Renly/Joffrey/Tommen, Sansa and Joffrey/Loras/Willas/Tyrion/SweetRobin/Harry, Daenerys and Viserys/Drogo/FAegon/Hizdahr/Quentyn/Victorian/Euron, Arya and Elmar/Ramsay, Robb and female!Frey/Jeyne Westerling, Cersei and Robert/Balon/Oberyn/Willas, Jaime and Lysa, Lysa and Jon Arryn/Petyr, Arianne and Viserys, Roose Bolton and Walda Frey.
It's astonishing how GoT had the two most prominent monarchs of the story, young, heirless, and unmarried not receive marriage proposals left and right from enemies and allies alike! Although it would have made the lack of a JONERYS!wedding even more illogical.
I really look forward to seeing Daenerys and Jon, respectively, showered with marriage proposals from enemies, allies, and neutral and unfit parties alike when she arrives in Westeros and he succeeds as KitN! Generally, I will welcome them being a thing and involving other characters as well, such as Tyrion, Arya, Arianne, etc.