Its a one off. When you're doing an issue that celebrates all the eras of a character in that issue's stories, no all of them will include the modern looks, not all of them will have the classic looks.
I've been a force for change. The trunks made little sense as time movie on, starting in the '90s-current. Now I'd agree that taking the classic look and ditching the trunks and leaving the rest alone would be a better idea, as much having a one piece armor or not suit that's all blue including the boots would be interesting too. But the ones that are from the New 52, Rebirth and Reborn, DCEU, games, etc. have been great. So they have been doing a great job.
The more you fight for the trunks to come back just to have them, the less credibility you have to be taken seriously. Not just from me, and others who disagree with you; but the DC/WB as well who all look at you as lunatics. Which for us who want to be heard, it ruins our chances speaking good things that need to be addressed because its buried by crap like the "bring back the trunks" nonsense.
In other words, stop it.