The main thing is don't get hung up on finding the perfect brush, that's a dead end. After half a year you should've already noticed that the problem isn't the tool itself, but how you set it up. A standard round brush with the right settings paints just as well as expensive downloaded packs. Try experimenting with the Shape Dynamics tab - that's where you adjust how the brush size changes depending on pen pressure and tablet tilt angle. Add Color Dynamics if you want the tones to shift slightly while you're painting. That'll immediately make your strokes look more alive.
As for downloaded brushes - yeah, some packs are actually decent, but often they're just pre-made versions of the same settings you can make yourself in a few minutes. The thing is, every artist has their own way of painting: some people need soft blending for sculpting a face, others want hard transitions for textures. There's no universal brush, but there is a universal method - make a brush that works for you.
Photoshop handles this perfectly fine, no need to switch to different software because of it. If you ever try Procreate or Clip Studio Paint - the brushes there really are prettier and more convenient interface-wise, but that's a matter of comfort, not a fundamental difference. Spend a week learning the settings, and your portraits will look way more natural.