

Cleaning is a good suggestion. I’d start there.
Also, that kind of looks like the cheap black textured plates that come with some printers. I thought the people talking about pei sheets were over-hyping but honestly they are really much better. It’s not a silver bullet but pla sticks soooo much better to them.
For pla it’s overkill, but for tricky stuff build adhesive can help. I had good luck with vision miner. It’s expensive but it’s been buy once, cry once because it has lasted a really long time.
Couple of thoughts.
First, what you described sounds like most of the toys I’ve bought my kids growing up so if it brought them joy, probably about as valuable as anything else.
Second, my experience is a bit different. My sons have 3d printed nick nacks displayed on their shelves and both have fidget toys they play with on the regular. Also I’ve got a chain fidget in my pocket I’ve been playing with all day.
I’ve also got a box of less successful toys I’d love to recycle if I could but definitely some wins too. So I think there are a lot of toys you’d be right about but also a lot of them are actually pretty interesting and fun to the right person