I often wonder if my obsession with speed is helping me forward, or holding me back. (I'm working on https://www.nslookup.io https://www.nslookup.io on the side

I often wonder if my obsession with speed is helping me forward, or holding me back. (I'm working on https://www.nslookup.io https://www.nslookup.io on the side.) There's so much else to be done. Will users really care enough to come back? Is a 20% speed up worth more than a better design or an additional landing page? I don't know...