It made them more formulaic, sure (along with the rise in syosetu and other webnovel sites), but the ideas were around for a LONG time beforehand. MÄR and Zero no Tsukaima
came out like a
decade before Mushoku did, and those are way more trite/tropey (and popular, honestly) than Mushoku. Hell, if you want to go further back there's stuff like Vision of Escaflowne which also do the whole "taken to another world" bit, or even Inuyasha if you want to stretch the definitions a bit.