There's also a little problem with wars with the AI today.
You can literaly wait them out in a neighbouring system, build massive fleets and retake world they invaded; most of the time after a couple active strikes they will "glitch" into permanently bombarding one planet and not doing anything else while you can do everything you want, increase war score, and win.
With 500 military power and 12 assault transports I ended a war that was declared on me by getting one planet, even though the war parties had 2K combined and bombarded two planets on three intensively (the third one I used as my "make space great again" factory).
Also you can easily wait out with -100% war score, no penalties, and the player greatly benefit from this in the current meta.
I would say the bad AI in war and the lag in big battles end-game + the lack of content are the three great bane of Stellaris today. Still enjoyable, but maybe in a full human player MP + 1-2 advanced empire?