First off, one of the complaints against ending de minimis is that it will reduce volumes. More expensive means fewer sales.

Secondly, with de minimis in effect, part of the process was having to check for (and catch) packages that were subject to duties which were trying to evade them. Now, everything is subject, so that can be eliminated.

https://pe.usps.com/text/imm/immc7_001.htm

Third, as noted by the video linked, CBP has advance info on all shipments, and now carriers will be expected to have paid before the shipment is received. It then will still need to go through the process in the video. So, no change there, but possibly with lower volumes and better paperwork. More orderly. Might actually speed things up?

Here's how it was 5 years ago. 8 minute video:

https://m.youtube.com/watch?v=DoY7SxrzNTc&pp=0gcJCfcAhR29_xXO