The fact that Donaire is still on the top ranking even at his current age, that's the reason why he is still getting good opportunities like this.
Regardless if the promoters wanted to see him in the ring or not, he is really bound to have a mandatory fight.
He's not being challenged though by young boxers but just doing the task he was assigned for.
Correct, he was able to still maintain hist status because of the high level of fights he got and the results, all of them are either TKO/KO except Inoue. So then the promoters likes Donaire for being that, representing their organization as a champion and that's why he is given another chance again for the WBC bantamweight.
And Donaire is not taking this fight lightly maybe just because the boxer that he is going to face is way below in the top 5 of the ranking. He is still going to be a threat to matter what but Donaire will be ready.