why exactly is izanagi better than balrog?

i would also like to know why it is better than phonoa, aka why it is top 2 (if possible)

The main threat in stages tend to be protected by a backliner or at least decently high range unit, and if they arent the main threat the stage tends to be fairly trival without them. If you have used naala you know how strong they are, since they have have ~5 times the dps of naala. If you want a different comparison, imagine if tecoluga hit the frontline, the backline, and the superbackline all at the same time w/o risk of getting cock blocked, while also having better survivabilty, damage, cooldown, and range (assuming all pierce is used).

Additionally since they hit the backline single target isnt really much of a hinderance since it doesnt prevent you from hitting the main threat (along with just hitting three enemies since its multihit).

They have very different usage compared to balrog, since balrog can only hurt the frontline + isnt meant to live long, unlike izanagi who is a midranger/sniper.

As for phonoa, izanagi is generally a lot more impactful since they have ~twice the dps and is a lot bulkier (3 times the hp and half the repositions) so they can tank things better. Even if phonoa lives longer izanagi will make a bigger impact in the time they are alive.

On top of all of that izanagi also has summon which like a breakerblast + slowbeam with damage at the same time which pushes his burst potential even further along with improving his survivability.

the only advantages grog has on izanagi are spammability, cost, and strengthened dps