I wouldn’t hate the leader cap if the leaders themselves were interesting at all, but they are literally an exp bar with a couple traits and an age. I realize Stellaris is not and never will be CK2 in space, the scope of Stellaris is really a bit bigger picture than that. But something interesting about them would be nice. Occasionally one of your leaders might ascend to be a Chosen One, or find a Towel (far more rare event than you’d think) and you’ll remember them. But otherwise you roll your eyes when they die and hire a new one.
The new update is looking really amazing though. I know I’ve said it before that the death of the tile system is the best thing that the game could use. Diplomacy is next. I doubt it will all be covered in this next expansion, unfortunately as the scope of these changes seem quite massive. It will be quite a ways off because they release a cosmetic pack and a story pack between each expansion generally, and this upcoming expansion I’ll be surprised to see before mid November.