So I'm really glad you're looking for feedback on the movement system, because I ended up going very in-depth with coding a dash mechanic for my game, and I think I know why it feels "off" to both myself and others based on comments. When I made my dash, I started with a basic Lerp from starting position to ending position for the dash, but it felt very clunky and (correct me if I'm wrong) it feels like that's the way you've implemented your dash here as well. It feels clunky because dashes are supposed to flow with your basic movement - if you're suddenly propelling at a higher velocity then resetting to your normal velocity instantly afterwards, it's gonna feel awkward.
So instead, what I ended up doing was using Unity's Animation Curve (https://docs.unity3d.com/ScriptReference/AnimationCurve.html) - it lets you set up a graph with your X-axis being the t value from a normal Lerp, and the Y-axis being the scaled result after evaluating through the curve. Basically, it lets you make your dash a lot smoother so you could do something like have your dash be slow for the first 10% of it, then ramp up to really fast 80% of the way into it, then ease off for the last 20% (just as one example, you can adjust the curve in the editor and play around with it until it feels right.)
I hope I explained it well enough, but if not please let me know, I would be happy to walk you through it!