I don’t know why is part of the new class post… but also having trees makes each class talent combinations wildly more variable than the refined 3 choice of VT2 classes (that also had nice built in boons) Balance is also numerically much more challenging with trees.
If it were a direct comparison you could pick Kerillian and mix and match her 3 classes into 1 with a tree.
This is a popular sentiment many expect the 5th to be a Mechanicus, except the deep Mechanicus main Lore fans.
Here was my attempt [New Class] Tech Priest - Warhammer 40,000: Darktide / General Discussion - Fatshark Forums