Having the last 1/3 go from the situation with the situation with moeka (who I consider to be the worst introvert character ever done in any piece of fiction btw) to "lets go on dates" with the side characters is a terrible form of pacing. The story had become emotionally gripping and tense where I honestly had no idea what to expect next when I was on the part dealing with the Rounders but I didn't think it would be "lets go on a date with the cat girl"
And then there's Shouichi who was just unacceptably bad.. This guy watches his daughter get accidentally stabbed and he just goes "hahaha fools!" and runs off, like really how cliche can you get? I've been told that it's actually really deep characterization and that he was really in shock, which completlely ignoring the fact hes carrying around a hunting knife and is willing to attack students almost at random with it I'd say seems pretty unlikely. If I recall properly he even attacks his daughter with a screwdriver or something. He fails as a father, fails as a scientist (apparently he had never heard of the concept of peer review before choosing to be a scientist) and fails as a functioning human being. It doesn't help that Okabe's great plan is to let someone stab him (brilliant! /not) and Kurisu is just standing off the side the whole time going "no daddy no!"
The show lacked any kind of decent villain. Moeka and Shouichi are 2 of the worst characters I've seen in fiction, the Rounders stop playing a roll partway through and Sern is just some organization in the background we know hardly anything about and that can't effect anything directly by themselves. All we know is apparently they just can't get this time travel thing down.
The contrived nature of the ending also upset me. Everything just works out disgustingly well for the goodguys and then the villains get what is coming to them, Okabe gets the girl who magically gets all her memories of other timelines back because the story said so and everyone goes about their happy lives (sept Shouichi of couse because screw that guy)
Then there was the movie which added nothing to the series and just ended up wasting time. It introduces a completely new problem involved with Okabe time traveling and solves it by the end changing nothing in the process... There's nothing I hate more then a story that is so blatantly pointless.
The only half decent thing I could say about the entire last 1/3 of the series is that I thought it was sort of cool the Okabe was essentially tricking the timelines to add up.
I don't need there to be some giant twist at the end or for there to be an epic battle. What I wanted was something that was thought provoking and helped pull the story together in a meaningful way at the end, which is what I honestly expected going into the series considering the rave reviews but I didn't feel it had either of those things. I had hoped for an ending along the lines of Shin Sekai Yori or the Zero Escape games where you can spend hours upon hours thinking about the story and how it all connects in the end but Steins;Gate feels more like standard goodguy gets the girl and wins the day sort of nonsense which I can see why some people like, but to me it's lazy on a series that deserved more.
It doesn't help that I wasn't really invested in Okabe ending up with Kurisu at all.