honestly, don't fall for the bronze meme of you having to play every role
I main adc (and with a small and generally monotonous pool of champions i'm pretty decent at like most of them). But I can't play other roles nearly as well. Doesn't mean I can't mid top jungle support, it just means i can't solo carry on them like i can my main role. If you're looking to play mids because you like anivia and ahri just look to invest your time in all the possible and good play styles of mid. Then, when you can, play other roles and just be minimally proficient at them (doesn't mean you can't be better than that, im a mean support and mid) but don't look to be as good at all roles equally
tl;dr invest your time into mid lane because you natural gravitate to them and be able to play the other roles at the minimum where you can be useful on them and not feed.
or at least that's my hardstuck plat 5 opinion