I also have totally believed ageing was the reason Kendall's kids aren't on screen, but they're still mostly invoked in the most recent season in a "you never see them and don't care about them" way. It's not really a retcon but I thought it was interesting that they were kinda lumped into the show phasing out anyone younger than the main characters (some of them definitely as retcons). You'd think there'd be something to explore about the adult kids, constantly questioning their loyalty to Logan, having their own heirs to worry about or fear.

Generally I don't think what I said about Logan's dementia was wrong. It's the catalyst for the start of the series, and the first season plays with to what degree it's a real concern, but once he announces he's staying on and the show shifts to merger storylines, or Shiv and Roman getting moments in the sun, (outside the 'cat under the chair' episode) Logan's not pissing on carpets anymore or making business moves that seem less than calculated.