I think I found out what was bothering me in Arcanum.
There seems to be 3 types of "things":
- technology (realistic, fully possible technology) example: steam powered cellphone :)
- fantasy technology (impossible, but makes sense/could be possible if, generally something that has explanation in science (even if flawed or if it ignores some "less important/unknow laws)) example: Frankenstein (body is commanded by electrical impulses from the brain (true), so if we apply a lot of electricity maybe the system will "restart" (untrue)); Jules Verne "cannon to send people to the moon" (true) but it ignores the acceleration forces (impossible, passengers will arrive dead)
- magic (impossible, not based on science at all) example: mage casting a fireball
I personally find the first two (technology and especially fantasy technolgy) perfectly fitting the steampunk theme. But magic (like elves and casting spells in Arcanum) makes it akward for me.