prequel by solving the mystery

Yes, just like Phantom menace, answering all those burning questions that no one asked or cared about.

does or does not do the original a disservice

It does since this was Matthijs van Heijningen Jr. first and last movie as a director, no character development, no memorable score, bad acting, terrible ending, bad CGI, receives mediocre reviews critics and people on IMDB, RT, Metacritics and basically everywhere else where people can review a movie, and bombed at the box office. Not that reviews matter of course or box office, on Reddit nothing matter because everyone's opinion is valid and you don't need to back it up with anything as long as you liked the movie. Then we also have screenwriter that has written such hits as A Nightmare on Elm Street reboot (that is getting another reboot because last one was sh*t) and Final Destination 5 which was final nail in that franchises coffin. Than also completely stupid and undoubtedly greedy decision to call this movie The Thing, just so you would think it's a reboot, which I did since there is completely no indication when this movie was marketed in 2011.

Only reason anyone would argue this movie is not a failure is because it's shoot in glorious bright colors, which help forget about what you are watching has boring one dimensional characters, offers completely nothing new and despite being a "prequel" is also about an crashed alien ship that has an alien in it that can assume any shape or form, which is 1951's version all over again.

I'm sure they meant for it to be both things at once and took care to make many details fit in a way that would work within the context of the John Carpenter film.

Many details like a dog and an explanation that John Carpenter didn't want to show. Like Christopher Nolan making a prequel to Dark Knight with Jokers origin story, this movie should never be made. Putting in a trash movie in a franchise that did not need to be touched, especially by no name director that has no previous experience except short movies and cheapest script writer they could find, jump scares, bad trailers, bad posters, bad cinematography (framing, color palette, editing), everything was cheap and lazily done, no matter if director actually cared about 1982's and recreated sets and filled in the gaps, so did Terminator: Genisys, script was still bad, there were no original ideas and this was made only for money. You can spot movies like this a mile away, rewrites, re-shoots and months after this movie comes out everyone forgets about it except for people that are unwilling to actually look at this movies as what it is: cheap marketing scheme based on nostalgia and elevated by movies that came before it.