Seriously I don't understand the issue. On iOS 15 if I swiped up to enter my phone while notifications was on the lock screen, they also disappeared once the phone was locked again.
And for the new system, once again, I just think people in general don't like changes and just want to go back to like it was instead of trying to understand or learn the new way. Honestly nothing really changed aside now the notifications are displayed on the bottom and you can chose between 3 options. Of course if you chose "count" you have to be more careful, but its just up to you. If you chose stack or list, you really don't miss anything.
I have to say that I only turn on notifications for stuff I really care like messaging, Uber, News and YouTube app so notifications are easily manageable for me but honestly I don't understand all the negative about this.