Right off the bat, it has to be acknowledged that by the time Savitar entered the scene in season three, there was a speedster fatigue. We'd seen Team Flash go up against Reverse-Flash and Zoom already, and there's a definite argument to be made that yet another speedster big bad felt redundant, something that the fourth season has rectified by the introduction of The Thinker.
That said, despite not living up to the level of hype that his predecessors had, Savitar did bring a few new interesting things to the table, particularly with the future death of Iris by his hand giving the season a goal to work towards, with a ticking clock element that hung over the team like a specter. Even further, his mere existence represented consequence, whether it's that time remnants shouldn't be treated disposably or that Barry should keep his abilities in perspective.
Now, say what you will about how he ultimately wound up - after all we'd seen him capable of, he got taken down by a bullet from Iris - but he did leave a mark on the show, from killing HR to taking advantage of the events of Flashpoint to restore powers to people, which allowed Wally to become Kid Flash. Compared to the big bads that came before him, he didn't quite raise the bar, but his impact is something still worth acknowledging.