I'm super glad you like the UI and elements of WebWave, thank you very much :)
But I'm concerned about you saying that WebWave is dead slow. Do you mean that the website builder interface is slow, like freezing while you're designing your website? We haven't ever got complaints about that from other people, so I suppose it's a local issue. I'll be glad to help you solve that
But if you're talking about published website speed tested by google page speed insights, websites created with WebWave usually gets scores of around 60. I know that's not superb (we're working to improve that), but that's not dead slow either. You can find some example websites here, https://webwave.me/made-in-webwave and test them yourself. If the website you've created got a lower score, maybe you've inserted some huge image that could not be optimized? Please run an automated SEO optimizer tool (that's available in website builder) to find out for obvious problems. If that doesn't help. Please contact our online chat support (we usually respond in less than 60s, so you wont wait long), or contact me directly via a DM on Facebook. You'll find me on our Facebook group here: https://www.facebook.com/groups/webwaveen

We will help you fix your problems, since I'm sure what you've described here is not a tools problem, but some other issue.