And opponents in Atla usually required force to deal with. Opponents in Tlok drew power from class support
That is the whole point. Aang wasnt suited to deal with the enemies on his show just as Korra wasnt on hers. Its the main point of conflict.
If swapped Korra wouldnt even have run from the temple as a kid and would have killed Sozin when she was like 14. If you put her start point to the iceberg she'd still have gone straight for Ozai and slammed his skull in as well in like 3 months or less
And Aang would have defused the whole Equalist and Red Lotus deal easily, and mediated the spirits with ease easily winning out over Unalaq.
And even if the Red Lotus still required forced to deal with, Aang would have been able to stop the whole Earth Empire/Kuvira issue to grow to those heights in the first place.