Describe how they "don't fit." The fuel line size, quick connector size, type, and orientation have to match.
Cut and splice is how it works. The splice is inserted into the existing line by using a hot blower to expand it and the repair piece, when it cools, it shrink fits and seals.
Those nylon tubing repair kits are common, but nobody said the makers have to do things the same way, there's at least a dozen different ones. Some of the older pre- alcohol cars use rubber hose - if that's the case, use only late model replacement hose for the modern corrosive fuel we pump today, or it will just fail in another year.
It's not rocket science, but it's not just any hose connector, either.