Disclaimer:
(This tier list was created with ranked and tournament play in mind but is ultimately a culmination of my own personal opinions and experience with the game and its characters).
(I will go into detail on my reasoning for specific gods and for the S and D tiers to explain why I think they belong there).
Tier breakdowns:
S Tier - This tier consists of gods that are performing far above average, when played in recent tournaments they were picked or banned frequently, they are also all favored pretty heavily in ranked play.
Aladdin has insane scaling and late game can completely rip apart a team single handedly with nearly any damage build.
Ullr is in a similar situation where his numbers are simply too high along with being able to abuse items like Tekko-Kagi allowing him to keep 100% uptime on the items passive.
Ra has an aspect now that turns him into an unkillable monster capable of burst healing his team and providing buffs. With the aspect he can now attach his 3 to others to consistently heal them without worrying about positioning and his ult burst heals any teammates hit.
Hecate would probably be the most controversial in my S tier as she requires a higher skill ceiling then the others to pull off but if you get ahold of her she can make team wiping plays with her large AOE ultimate and AOE abilities.
A Tier - This tier is comprised of characters that perform better then the average god. Most of these gods are highly contested in ranked play with a few hot takes here and there.
B Tier - These characters I find to be for the most part fairly balanced and where I would consider average in terms of balance. They are picked relatively frequently in ranked play.
C Tier - These gods fall below average in terms of ranked/pro play or are very niche picks requiring one or multiple other characters to synergize with them. Yemoja you could argue should be multiple tiers higher but I find her to be less impactful then the other frontline supports in most situations.
D Tier - These gods are just bad unfortunately, luckily I've only felt that 2 characters belong in this tier which in my mind is an indication that most characters feel pretty dang good to play!
Sol has been nerfed one too many times in recent patches and is now simply the weakest ADC, her abilities scale off of intelligence and the ADC int items are not in a viable state so you are forced to build strength, the problem with this is that her passive doesn't allow her autos to slam as hard as they did when crit was broken, in contrast Zeus the other mage ADC in the game has a passive that still allows him to pump out numbers.
Cabraken was the most recent release and therefore might not belong in this tier, however from the few games I have played with him alongside community sentiment its obvious he is under tuned.