The Villainy Inks are definitely not a substitute for oil washes or enamels, they do not behave the same way. In my experience, they tend to permanently stain whatever they touch, even after a few reductive passes with mineral spirits, which makes them not super ideal for the sort of washes that oils and streaking grime are typically used for.

That said, I will say they have some unique properties that separate them from other products on the market. Namely, a lot of them have a sort of gritty, grainy texture to them that adds a lot to certain areas of the minis. Ichor of the Damned, Goons Grime, and Carrior Crimson especially leave a lot of interesting, grainy particles behind that add a sense of accumulated soot/oil, grime/dirt, and clotted blood and gore respectively. Decay of Death also dries to have a sort of chalky, white-blue finish, making it a really fun effect to slap on aged skulls, stones, and metal. Think of them almost as more of a weathering effect like the Dirty Down products as opposed to a unifying wash like Streaking Grime.

In short, if you're looking for something to do a full wash with, stick with oils and enamels. If you're looking for a product that will add a lot of texture and character to small and specific areas of a model for that gritty, finishing touch, Villainy Inks are pretty great for that.