Not knowing how an app or a plug-in works is not a basis for a bad review. If you can’t take the time to understand how something works, I do not want to read your instruction that I should not buy something. In fact, I don’t want to read any review that tells me what I should do with my money.
I’ll give reviewers some instruction, because apparently it’s needed. Unfortunately, it’s needed everywhere (not my job), and not just for this niche product.
Recommend a product or don’t, tell us your experience with the developer’s work, compare the product to other things if you like. That is, write a review - not invective, not frustration with your own misunderstanding, not support requests (or demands), not point bribes, and most certainly not imperatives about the buying habits of readers. This kind of stuff wastes your time and ours, it’s out of place, and it is frankly unwelcome.
On the product, it works, it behaves in the expected way if you understand old-school vocoders, and it may or may not be what you imagined if you have no experience with such equipment. There are resources available to explain the use of this effect. Please bring yourself up to speed and get the product working before you review it, because otherwise your review will join other irrelevant and misleading reviews here.
On the developer (who has been attacked here for no obvious reason), many people - including most of the longtime musicians using software on this platform - find this source both reliable and valuable. A given user may prefer other developers, but this one is well-regarded and responsible.
Potential buyers should think about whether an analogue-modeled vintage vocoder fits into their music and workflow before purchase. Digital vocoder designs based on FFT tend to be more straightforward to use and give a wider range of effects. Generally we look to the analogue types on which this one is based for the particular qualities of the sounds they give and the gentle-yet-strange transients they produce. The palette is more limited but special in its characteristics. Check examples of music using vocoders from the seventies if you’re not sure about the sounds you can coax from this kind of machine or software.