Slow Export with simple Fusion Comp in Resolve

so i was just rendering a little section from something im working on which includes a adjustment layer on which some fusion stuff is happening. nothing fancy though. basically a few merges, transforms, backgrounds and a text layer. no motion blur, no keying. so like i sayed, nothing fancy.

but when exporting i get about a frame per second.

at first i was like: well, guess a i9-9900X + a RTX2070 just isn't cutting it. i mean there has to be a reason quadros and xeons exist.

but than i took a look at my task manager and i noticed that really only 1 of my 20 cpu threads is doing something. guess the others are on vacation on the bahamas or something like that, together with the gpu who chills at about 15-25% workload.

does anyone know why? is it a bug? is there something i can optimize in the program settings?
would love to see at least one component in my pc at 100%. because even if i would want to upgrade my pc i have no idea what i would upgrade because there is no obvious bottleneck for me.

any suggestions?