Let's be honest, they're probably saving auto trace, shapebuilder, and line weight tool for version 2. The guys at Serif have proved that they are excellent software developers capable of solving problems and implementing new features relatively quickly. These are the main things keeping Designer from being a near perfect software.
If they give us these features now, what else is there to entice us to upgrade to version 2 when it rolls around? The performance is basically perfect, all other tools are there, and it already beats Adobe Illustrator in a few ways. They already have programmed these features in the past with DrawPlus X8, so they certainly have the skills necessary to program them again.
I do not blame them for putting off these features. I sometimes grow a little worried about Affinity's business model, and if they are going to stay afloat. With such a low price and free updates, it amazes me that they can pay all of these fantastic developers. Some time along the line, they will have to raise their price and get people to buy their products again. And, if version 2 has these features, I will gladly pay $75-$100 for it, especially if it means keeping Serif afloat.
Additionally, I feel confident that they will make my $75-100 well spent. I have no doubt that they will make the auto trace and shapebuilder etc. as good as they can possibly be. Frankly, if I had the money, I would be donating to Serif. Adobe needs competition.