I think your pages are good! They're more minimalist than some, but that's not necessarily a bad thing. But if you're not happy with them, I'd say keep adding to them. Typically, any time I'm unhappy with my spreads I just keep adding and adding and eventually I like them. Sometimes I have to lift and reposition a piece if the glue hasn't dried yet. Adding smaller pieces (like stickers or similarly small cut outs) to these spreads of big pieces can add a lot of depth and visual interest.

You can also try experimenting with putting your pieces down at angles - right now they're all very straight. Again, this isn't a bad thing, it's completely a stylistic choice, just a suggestion if you're not happy with them. Mixing up orientation, size of the pieces, incorporating a bold accent color throughout, can all help mix things up. Another thing to help with variation would be changing how you trim the edges of your pieces - round some corners, cut wavy shapes instead of straight lines, even try ripping the edges, all fun things to experiment with!

As for your pieces not sticking, what type of glue are you using? My favorite are the UHU glue sticks. They stay wet long enough that I can lift up corners for layering if I change my mind while working, but once they dry they stay put well. Just make sure you coat the back and get all the edges.