Right now it is nearly non-functional.

Just using an example from one of the more popular games, searching for "drnose" will not bring up the user "mrdrnose".

At this point we're better off using google to search for games on this website

Could be better. But try https://itch.io/search?q=mrdrn

It puts emphasis on word roots and word beginnings. And on words. And on projects. It is not a substring search.

Try 

https://itch.io/search?q=mr+dr+nose

I works with relevance it seems. And mrdrnose has no relevance for the every day word nose. And drnose is not a word, so nothing could accumulate relevance for that one. And of course mr, dr, nose are three words, and mrdrnose is one word, relevant only to itself.

As for relevance and focus on projects, uhm, type v o i d in the search box. No enter.