So I've heard a lot of complaints on YouTube about the cardbacks and I fully understand and agree with the comments, but there might be another reason why the cardbacks are so flimsy.
supply is short, demand is high. Nothing new.
The regular material might actually be unavailable at the time needed.
As most people are aware, many raw materials around the world are in short supply and paper and paper products are some of those items.
I work in the print industry and I can tell you that right now there are major delays in getting regular stock items.
Lead times have gone from 3-4X the usual turn around locally and if you order from overseas costs have gone through the roof (e.g. ordering a container used to cost about $5,000US and can now range into the $20,000-$35,000+ for same container, at least in my experience) and oversea lead times can add months to a projects completions. (e.g. Look at the number of ships out west delayed trying to get into harbours and offloaded)
There are also capacity demands and market limit restrictions, that are happening at the manufacturers (mills).
More importantly a massive increase in online sales and shipping the last couple years which have exceeded the industry ability to produce enough packaging material. (side note: many companies are making the transition to new packaging lines as they have seen traditional printed paper usage decline.)
As such printers have had to find alternatives to their regular products including stocks that might be lesser quality but are at least readily available.
Printers have seen price increases ranging from 5-8% and sometimes more which then costs about the same as the old stocks pre-pandemic.
If you have MRSP for a toy you need to make sure everything fits into that budget and when it can't you have a couple of choices: you cheapen the product in some way, or you delay your product, or you raise prices.
All in all it just show how intertwined the economy is. Anyways I'm sure there are other reasons but wanted to bring my perspective. I totally admit I could be completely wrong

but this makes sense to me.