I am currently sitting in LAX en route from San Jose to Cincinnati, where I am giving a talk. I have concluded that LAX holds a record. It is the worst marked airport in the world. It's true that I have not actually been in all of the world's airports so there may be one somewhere that is worse, but I doubt it.
I arrived on Delta, was to leave on United. The Delta terminal had, so far as I could tell, no signs showing what airline flew out of what terminal, no signs showing how to get to terminal 7, which turned out to be where United was, no visible information for any non-Delta flights.
I succeeded in finding my gate by asking people along the way. If I did not speak English—and a lot of people coming through LAX don't—I might still be looking.
LAX is currently under construction, which can explain some problems, but not this. It would be easy enough to make up a signboard showing which airline was at which terminal and put one in every terminal. It would be easy enough to put up signs showing, from each terminal, what direction you went to get to each other terminal. But nobody has bothered, judging at least by the Delta terminal and most of the space between it and United.