Nobody is claiming Rush is the hottest prospect around, by any measure. Just saying he managed to be reasonably competitive where Dak failed to get the job done. I'm not claiming he's better than Dak or anything of the sort, but it's fairly obvious that Dak isn't the best version of himself at this point in time. It will take some time for him to recover before he ready to return to action. He'll need maybe a few weeks, at least.
Rush is probably better prepared to be our best backup, whereas Lance has time to go before he's ready to compete with Rush on an even level. I think Lance needs considerably more experience to be prepared to take Rush's place as Dak's backup if he's ever prepared to vie for that honor at all. The Cowboys also need a better prospect than Rush as Dak's successor, imho. Now, is that real enough to suit you?