I agree with OP on the issue of technology and growth, it really makes no sense that tech is "random" and, to those who think making it a standard tech tree would make everything the same every game, you just have to choose to follow a tech path every new game to make things different, if people really care about different options they will be able to make do with a standard tech tree and their own choices.
On the issue of growth, it really doesn't make sense that species with lower habitability would grow faster than ones with higher hab just because, it should be determined by a calculus involving habitability, rights, avaliable jobs (you could take it a step further and add the species traits that have synergy with jobs to it as people would like to go to a place were their abilities are best put to use) etc. instead of just randomly picking one to grow as it seems like is the case currently.
I have, however, to desagree vehemently on the issue of leaders. Leaders are people like you and me, they make bad decisions and sometimes it fucks their lives over, its just the way things are, its part of the empire experience stellaris is trying to emulate and i think removing it would be a loss. In fact, i think leaders should have a larger spectrum of traits to show better the human element in this game, i hope it arrives one day.
And to those who believe stellaris is all about randomness, i think you guys are projecting your own particular preferences into the wider player community or the devs, the game isn't mainly about randomness, nowhere it is advertised as such and, like the majority of the paradox playerbase, most players i see come here to rp the imperium of man or play microsoft excel with kino visuals, many would actually disagree with the idea the game is all about randomness if you asked them. Not that randomness doesn't have a very important place in the game, i believe it has, just that sometimes it hampers the experience, the tech and habitability being examples of such.