I still play Civ 3 and 4. Might splurge on Civ7 with this going on.
In theory, there's still reason to spend time on the colosseum: with enough ELs you bypass gearing below g12, which means vastly reduced kyro expenditures, while the kyro gains remain steady... thus you have more kyros to trade for r10 mats.
But I'm already going to be hosed on r10 progress because spenders will now dominate my shard and the increase in rewards for the heaviest spenders is silly. 10th place receives 10x the rewards of 91st place and 20x the rewards of 251st place.
The difference is too extreme, so I'm not going to be worried about r10 anyway. And if I can't earn r10, then there is no reason to play the colosseum. What a waste.