I'd say that is probably related to having 3 layers. Although sometimes you need more than 2 layers, it has to be pretty damn cold, because you are almost inevitably going to soak in more than 2 layers due to the inability to breathe. Better to have a thicker baselayer, if you have to, then you can at least unzip the jacket and expose it, when you are starting to sweat and get warm.For the top I had thin long-sleeved synthetic sweatshirt, then warm Merino mid-layer and finally softshell jacket. The jacket was made for XC skiing, it was uniform (same material everywhere), back was heavily perforated, but most of the perforation was closed by backpack. Temperature wise it was ok, but there was moisture buildup.
Primaloft isn't very breathable when thicker, but that also looks very thin, so it's probably decent. I have a primaloft puffy that I occasionally use (down puffys are much warmer and lighter for the weight) and I put it on when I want to get warmer, which at that point means trapping heat. I have a cool backcountry jacket with thin wool insulation I got last season, works really well. IME, few "MTB" jackets are really doing it right.