I agree with @catwriter that if some bad seller starts making fake orders and cancelling them to hurt a good seller, the good seller can report this to CS. CS will notice if there are suddenly a ton of new cancellations for invalid reasons. However, I want to add that even if this weren't true, every seller has to utilize every opportunity to get attention to their own gigs in spite of cancellation rate or position in search.
There are simply too many sellers on Fiverr now to display everyone in the top few pages of search and it's been that way for awhile. Some sellers have really panicked about it and blamed it on conspiracies or discrimination, but there is only so much room in search for all sellers. Search isn't even guaranteed, some sellers who choose to sell services that aren't in Fiverr's current editorial focus don't have their gigs displayed in search at all.
Each and every seller can make use of all the excellent promotional tools available. Fiverr Anywhere allows for funneling from a personal website to a gig. getting involved in niche forums can drive views to your gig. For example, if you sell logos, you want to be in small business forums where entrepreneurs need low cost logos or if you sell dog videos you want to be in forums for dog lovers.
You can even hire other people on Fiverr to help you promote yourself, but it has to reach the audience that needs your gig or it's just useless. Those are just basics and some good marketing books can offer more ideas. Search will never be big enough to fill the needs of everyone who wants to sell here now.