Political scheming was always the core of the show, but it was also always set against the backdrop of the White Walkers who were a force of nature. The game of thrones is just that, a game, and the game is inconsequential against the force of nature that are the White Walkers.

But you're absolutely right that the White Walkers plot being resolved in one episode was a huge waste. Dany, who in many ways parallels the White Walker threat, had two seasons in Westeros proper before being defeated.

Realistically I think you need Dany to "give up" her aspirations for the throne (which we do see in the show when she makes a deal with Cersei) and spend a whole season fighting and ultimately defending Westeros (which again happens, but wayyyyyyyy too fast), and then feeling defeated/unappreciated takes King's Landing because she feels she's earned it.

Minor book spoilers/speculation

The book having fAegon will be an additional point of contention for Dany. Dany will make a deal with Cersei. fAegon will take King's Landing, freeing it from Cersei's rule. Dany saves the day, but now Cersei isn't in charge so whatever deal was made is moot. Also fAegon has the better claim. So Dany did all the work, gets none of the credit, and doesn't even have an evil ruler to overthrow.

But yes, skipping all the story that made the show interesting was a huge mistake.