In fact, Bitcoin Cash does have modified retargeting that drops difficulty much faster. (they could just have well dropped difficulty by 100 times at the fork, as well)
So you have useless tokens. Value is perception.
And should Coinbase then be obligated to distribute those useless tokens?
No of course not. If the tokens are useless then nobody will blame Coinbase for not supporting them. But we're talking about BCH here, which is bigger than all other coins save Bitcoin and Etherium. There's a LOT of money at stake here.
At what point do you know if it is useless or not? Who decides? How long should Coinbase wait to decide to support it..before it becomes useful or after?