Except you still get the at the very least soul rewards for playing Casual PvP as if you were playing on normal difficulty, despite the opponent getting the stat boosts for playing on your current difficulty - this is very easy to test. I haven’t mathed out gold to see if it gives the correct amount for difficulty on casual, since match 4-5 gold messes with the numbers, but the average base reward for gold on casual matches is always lower for me on Casual than on Ranked anyway. Opportunity cost from not winning points in a ranked battle is more likely to hurt you than the points you actually lose if you are vying for a leaderboard spot, so if you are going for a spot, you shouldn’t waste time on casual period. And if you aren’t vying for a spot, Ranked is better overall rewards for your time, because you get more trophies, more glory, and tier rewards. You can’t revenge, cant get rivals, you are still attacking the same defense teams, but with difficulty on - Casual doesn’t make your life easier, it makes it harder.
Either way, other than challenging yourself for lower overall rewards, its absolutely not ever “worth” doing casual in its current state. Might as well just do ranked and ignore your position on the leaderboard.
I’d rather have the other rewards fixed than giving additional trophies. Still wouldn’t make the mode worth doing for me 99% of the time, but maybe someone could find it useful then.