Probably not. Jirachi was going to be the best steel type only because Doom Desire is powerful and Metagross and Dialga had crappy moves. Meteor Mash went above and beyond expectations, so even if doom desire is “stupidly strong”, meteor mash is just ridiculous.
Jirachi, like Mew and Celebi, probably won’t be meta changing, but it could at least be decent. Charge beam is quick, and confusion is a good fast move. If it had a steel type fast move or a fairy type fast move (ugh), then it’d be even better.
If you don’t have 6 Meteor Mash Metagross then Jirachi could definitely be an addition to your steel team. Personally I like variation on my teams, so even though I have 6 Metagross now, I’d probably include a Jirachi, Dialga, and maybe Scizor (just cause I like it), unless I’m really desperate for premier balls.