The mobile design: I absolutely agree, I didn’t expect so many of our users to come from mobile as the target demographic is desktop developers. I see now that I may have misjudged things a bit. Future plans definitely include a nicer website with better mobile support.
Header: They won’t very soon, Pakkly’s still in Beta, some things are placeholders for future functionality.
The Steps section: Absolutely agreed, we are already working on a video explainer.
The Newsletter section: I thought it fitting into 100% of the viewport height made it distinct.
In regard to caching, we had a caching plugin but it caused some strange layout bugs so we disabled it, I’ll look into those, thanks!
This looks like a very cool project. I wish it was around before I glued together my current hellish multi-platform release system. I will dig into it before I require it again.
Header: why do the Sign In and Get Started links point to the same URL? Do you need a Home link for what's essentially a single page site?
The Steps section: could probably be better presented by a video above fold in the future to take far less space.
The Newsletter section: the white background and wide margins makes the section seem like it belongs to the previous section (Step 3).
I think you could use a WP performance/caching plugin to easily improve site performance. My favorite combo right now is Breeze and Cloudflare.