I've never posted on the forum before but I've got 500+ hrs in Stellaris and made an account just to add my voice to the chorus of disapproval of the new static leader cap.
I think it's a very roughshod system to achieve what the devs intended and in practice achieves the opposite. In the very first game I played with the new DLC, I realized I didn't even need an admiral for Minister of Defense, since the early game exploration was so peaceful. So I fired his ass and recruited another scientist. But what kind of empire doesn't have a Minister of Defense? In reality, there would never be a trade-off between firing your top military staff and hiring more scientific leaders. Now instead of roleplaying a game, I'm just gaming the system.
The basically static leader cap is just mind-boggling from any kind of roleplay perspective, which defeats the purpose of the leader system to let you roleplay. What, in roleplay terms, is this cap supposed to represent? Why would my leaders become dumber and less able to gain experience if there are too many of them? Why does this cap only increase with random traditions and technologies? Why do I need societal traditions and scientific research to know how to employ more leaders?
Unity costs make sense, as the roleplay idea is that too many ambitious and powerful leaders can become a political problem as they compete with each other and so on. What makes sense to me from a first principles perspective is that leader cap increases with empire size or pops or something similar that represents the size of your empire, the size of the pie that ambitious leaders can influence, while going over the cap costs unity as they begin to step on each other's toes. There's no reason the cap should be static unless you research specific technologies or take specific traditions, nor that your leaders become dumber and less effective if there are too many of them. IIRC we paid leaders with energy before, which also made sense, because ambitious people want to get paid. But this new system is just bizarre.
That aside, there is no way to paper over the extremely conflicting leader design philosophies in the game right now. I can mod the leader cap, but that doesn't really solve the core problem, which is that the game itself can't decide wtf leaders are and what they are supposed to do. As others have pointed out, hiring generals now is basically punishing yourself. Meanwhile, we still have these random envoys in the game, who still get portraits and names. Then, we've got leaders who simultaneously sit on the high council benefiting the whole empire with their skillz and knowledge, yet somehow they are also in the field excavating archaeological sites or whatever. A science ship is unable to survey a planet without a figure of such incredible talent and stature leading it. We have a hard leader cap, but the game taunts you endlessly with empty UI boxes for your dozens of fleets, systems, and so on.
Moreover, even the new DLC can't decide what leaders are supposed to be. Are they these epic heroes who stand out in history or regular competent people who must fill important positions? If ordinary leaders are epic heroes and so we can't expect every sector, fleet, and council position to have one, then why did we also get 2-3 new tiers of epic leaders via destiny traits, renowned paragons, and even legendary paragons. Meanwhile, the freakin XP and leveling system seems to indicate that leaders are in fact meant to fill positions, and the epic heroes are obviously only the ones who reach that stature through their careers, trait gains, XP gains, etc.
In the end, none of this meshes together. It's a cacophony of conflicting design choices. I don't know what the solution is, but this thread has a dozen smart ideas that could be part of the solution. Someone needs to take a long hard look at this and deeply rebalance this.
My personal preference would be a game with tons of leaders, like we had before, that allows the really legendary ones to make themselves known *EMERGENTLY* through doing things, not because the game tells me they are or hardcaps me to just a few who must necessarily be important since I can't pick any more of them. We have a growing cap that punishes you in a roleplay-coherent way, like unity or some other political factor, not leader XP gain. Empty UI boxes are telling you that you are being cheap with unity, not taunting you. This is literally the system we had a few weeks ago and it was great.
You know what would be really cool? If going over the leader cap created a small risk of a certain leader defecting and instigating a rebellion on one of your worlds to become independent. You could even tie it to leaders who are from non-capital worlds. I dunno man. Just give us something creative and that makes sense.