Think about it this way
Goku from Dragon Ball Z
Super Sayan was interesting since it brought him to such a level of power that he literally could not be beaten by any of his foes, so they made the foes more powerful. So how does one make a Super Sayan more powerful? Super Sayan 2, then 3, and each time his powers and hairstyle became more out there and stupid.
We already had the potential to destroy worlds. We started out calm enough, a single guy with possession powers and a couple poachers. But then all of a sudden we have escalated to Genetically Advanced War Machine Animals, Mind Control to turn us against eachother, alternate versions of ourselves. ALTERNATE UNIVERSES! How are we meant to exceed that? Eventually we will be summoning more and more AU characters because there is literally nothing on earth that could match us in levels sheer power at this point, we have proven ourselves capable against basically the earth
To keep scaling up, we would eventually in time go to massive anime fights, explosions, entire planets exploding. Its basically already possible
And not only Dasken
Originally Midnight was extremely weak, we were literally never going to have a plot point that happened at night
Now he is essentially a sun diety who can manipulate plasma (not that he is ever going to leave the sun for extended periods of time)
WE have characters who can summon wormholes to alternate dimensions
Ice, Fire, Air, Blood.