Sooo i have been playing my first game in stellaris, two dozen hours in, and the game now feels kind of boring. I play in vanilla, no dlc/mods, and maybe that's the issue, but that would be kind of sad.   
Anyways, I basically control the whole left side of the galaxy( i have 5 subjects), every bot is "pathetic" in every regards, execpt for fallen empires whose only superiority is technological. i feel like my 31 planets are all pretty much optimized or on their way to be, my economy is huge, i can't even sell my overflow of basic resources since even my rings cap is regularly reached. i juste won my 4th war against the federation formed by basically everyone else, and it is getting kind of boring. But the worst part for me is i feel like i can't even progress in techs anymore, in every branch i reached the repetitives,(like 5% shield 10x is getting out of hand). And i can't seem to find any new techs, despite my head of research in voidcraft II and computer, and used to have a fields, particles, and propulsion one for 50\~ years. So what is there left to do? in a few decades i will smash the federation, and then right after the fallen empires, but it is kind of boring to just do senseless wars with large but weak ennemies.  
I heard there were endgames crisis, but the victory screen tells me the game is ending in 2500, and i haven't seen a single sight of said crisis? I feel kind of lost and i hope i am not the only one in this situation.   
thanks for any advice or help on wether this is normal or not. 

I don't understand what is there left to do after mid game..