No film director ever sets out with the intention of delivering a bad looking movie.
It wouldn't make sense.
So, it must be devastating as a filmmaker to pump your heart and soul into a project only for it to be weighed down by a few (or more than a few in some cases) god awful CGI moments.
It must be said that designing computer generated imagery is no mean feat. It can take months or even years for visual effects teams to craft high quality CGI sequences for a feature and even then there's always room for improvement.
However, the likes of Avatar and Avengers: Infinity War/Endgame have now shown us what is truly possible when it comes to the world of CGI in film.
So, that's why it can be so painfully obvious when a particular effect doesn't stick the landing...to put it politely.
It doesn't matter if you've got a Marvel Studio backing you or a cast of living legends to play with, once fans around the globe spot a moment of terrible CGI in your movie you can bet that it will be near impossible to unsee that beat of badness from there on out.