Mid laners no longer taking ignite?

No just exhaust honestly has more kill potential sometimes. TP gets you where you need to be

Everything else is just more useful throughout the whole game, while Ignite can usually only secure kills in the laning phase. Exhaust can pick out a target, teleport can get you to wherever you have to be, ghost is useful for some champions (Viktor, Vlad), barrier can help keep you safe, cleanse is useful against certain matchups (coughLissandracough), and heal is a heal that gives you a mini speed boost.