Why does ignite still do so much damage

Ignite already does that. It lowers incoming healing for the duration.

Ignite was (at one point) losing popularity in midlane due to TP being better at the time. But imo Ignite was overbuffed. The damage it currently does is ridiculous, and considering the high-damage meta we've been in for so long this only adds to that problem.

Because assassins are just such skillful champions. We need to give them more things to make them easier.

Because noone takes it in e-sports. Mostly midlaners, but even they prefer teleport.

Because TP gives you a massive map presence and before ignite got buffed literally nobody took it top lane. Now it's a pretty fair split, honestly.

BECAUSE

MUH 200 IQ ASSASSIN PLAYS

Because there is counterplay to it in the form of heals and shields. Yes, it reduces healing but they can still make the difference between life or death.

Exhaust was nerfed repeatedly because it was simply always better than Ignite. Screw a bit of true damage early if you can have a spell that simply makes it so you cannot get killed by a person, while also having a lower cooldown and offensive uses as well.

Don't forget that many champs rely on this bonus damage to further and achieve their lead, something another summoner couldn't do.

I don't know. But hey, let's nerf TP. That'll force everyone who isn't a pro player onto ignite. Wait a minute...