"search by full title" this can't be the solution. Peoples must find the games with one word or tags and this isn't working. The site must fix this.
Viewing post in My game isn't being indexed.
Hoping that people would search your keyword title by accident is not a good strategy. That is what tags are for. Also, with your wording of "find the games with one word or tags", you apparantly do not know that there are two search boxes. The search box does not search by tags and tags are exhaustive results, if the games are not blocked by other reasons. Like being an adult game or not being indexed at all. The search by title results are not exhaustive. It is limited to about 60 results + exact title matches or something similar.
Itch could communicate this better. Making it more clear that the search is title search and on the results page, that this is not showing all results.
I'm telling you how search currently works. The systems has received improvements recently, but it's still optimized for people trying to locate a specific game. As explained in the Search&Browse FAQ, itch.io can't guarantee visibility for every project. Please make other plans as well.