I don't think I've ever seen the hyphenated "past-dweller" before, so I would have to answer your question of usage by saying it is not common. However, it is immediately obvious to a native speaker that it must mean one who dwells in the past, just as a "pond-dweller" would be a creature that dwells or lives in a pond. "Dwelling (or living) in the past" is a common phrase which means having old-fashioned or outdated ideas and attitudes, so while the term "past-dweller" isn't commonly used it is directly alluding to a common expression.
English allows for creativity in the use of both hyphenated and compound words. It is quite common for a product name to be created as a compound word and it should be easily understood by native speakers that it does what its name implies. For example, it seems obvious that a "dustbuster" gets rid of dust.
There are lots of synonyms to describe a thing which is "old fashioned", such as "antiquated", "outmoded" etc. The words I can think of to describe a person who is stuck in the past vary in meaning:
- Traditionalist - an advocate of maintaining tradition, especially so as to resist change
- Nostalgic - Someone who enjoys things from the past, not necessarily someone who resists them
- Luddite - someone who actively refuses to embrace new technologies
- Anachronistic - Someone or something that belongs to an earlier time period
- Fuddy Duddy - a person who is very old-fashioned and pompous.
If any of these, "nostalgic" could replace the term "past-dweller" in your sentence and is probably the most widely used, but it would not necessarily carry the same meaning.