I'm not going to defend how they're handling it but I will say this: there are 'reasons' (good reasons) to segregate processing normal/everyday routine new apps from fixing a backlog, if/iff you are reasonably sure the reason for the backlog was temporary.I'm getting the impression that the passport processing is also going roughly LIFO with the backlog, like the citizenship processing! October passport applications seem to be processed fast, while many from the summer are still waiting. Like how 2022 citizenship applications are being processed quickly, 2021 variable, and 2020 and prior very slowly.
"Good reasons" is from the perspective of management, of course, and depending on their own policies/priorities. They won't seem like good reasons to anyone waiting.
[Short form is different resources needed, long-term aspects like training, and use of physical space, etc. But mainly because of bottlenecks in 'digging out' from the backlog. Easier/better to make two separate processes, one for new/normal business, and one - temporary - for the backlog. If it helps to visualize, the backlog is a mineshaft with limited physical access and adding resources only slightly increases output. But if you have a new/underuitilized shaft - ie new applications coming in - you can get much better output.
This is just an analogy so like all analogies imperfect, if you think it's wrong, ignore.
But if you're just angry that your app is in the backlog - there is a reason, even if it's not beneficial to you.]