Being raised by Pokemon has become increasingly common in the fan fiction community for a variety of reasons after N came along, but I would not personally define it as a cliche yet. Legendary usage is a pretty broad topic. Most journey fics do involve at least one legend in some way. The exact method varies, but using a legend as a starter or the giver of an ancient prophecy that obviously applies to the main character and the main character alone are probably the most cliche ways of doing it and the first is generally associated with bad, bad fics. I've seen it done well, but that was in a semi-parody of the trope so I'm not sure that counts. Most other legend uses are uncommon enough to be not particularly cliche, if only because they tend to come in late in fics and most journey fics do not get to the late game.