If you get everything else right, you can get by on a wide range of dosing. At that point dosing is really fine tuning things. If you don't get everything else right, even the most perfect dosing scheme won't save you.
The other thing to keep in mind is to always look at the particular plants in a set up. A tank full of Rotala's is a lot different than a tank full of Ludwigia's and Limnophila's.
Selecting some parts of Greggz' quotes, what may be interesting in the evolution of more attention to detail in dosing may be due to the expansion of species we keep. It was easy to please what is now known as "simple" plants as hobbyists are constantly pushing towards discovering the next rare species to introduce to the hobby. The constant desire to just tweak things just a little bit to get that new favorite plant to respond while not dragging down others has, in turn, pushed us to experiment with all sorts of variables
Maybe the shrimp guys have it right. Don't mix some of those species if they require different water parameters. In that vein, I think even @burr740
has started to separate some things into different substrated tanks to get things to respond better. And didn't @Maryland Guppy
use solo cups of different substrates for this very purpose?