I totally get that a lot of homeopathy is absolute BS quackery. But there is absolutely some potential with herbalism, even though you still have to avoid the quackery. Good materia medicas exist, but aren't cheap.
The key is rigorous study, and this is where it is difficult because there's not a lot of profit motivation behind putting together scientifically rigorous studies for plants that anyone can grow easily in the home. A pharmaceutical company on the other hand can make a new chemical, patent it, create an array of easily prescribable dosages, control it on the market for a period of time, and use that period of time to recoup the cost of research, development, AND funding scientifically rigorous studies. No one is going to pay for a study to show that chamomile is a mild relaxant, you know? And this isn't anti-pharma BS, this is just basic business. No one is going to spend millions on research for something you can't patent. So, you get left with a lot of "well, there's little research."
Another problem with herbs though - every plant is going to be different. Each flower could have differing levels of active chemicals, so what do you call a dose? I respect groups like USP, but I feel like it is almost a losing battle considering how easy most herbs are to grow.