Toys with Doors

Sounds normal to me.

All mine did that at one stage or another.

My nephew right now has a bag with new blocks in it. He puts a block in, takes it out, etc.

Added: you know those old Tupperware shape sorter balls? toddlers love doing this stuff. It's a new motor skill or development for them. They'll do that over and over for weeks. That's very typical of toddlers. Are you concerned because there's not much imaginative play? Sometimes they abandon one type of play for something new they are doing that interests them. Completely normal. And not using toys as intended (for example you say he puts crayons in his toys with doors) is totally typical too.

Not all my kids were imaginative. I have one kid who rarely if ever did pretend play. He was all bounce the ball, stack and crash blocks, etc. He still used his imagination but not in as obvious way as my others. That's ok too. Different personalities.

My dd used to love the books with the pull tabs or little folding "doors" with pictures underneath. That might be a good option for him if all the big toys are too expensive.

Yep!
Very common.
Soon he'll be learning about zipping zippers, buttoning and unbuttoning, velcro will be a source of fascination (and really? velcro is pretty cool!).
Our son had to push a chair over to a door so he could climb up and examine how a chain lock worked.
They are all about learning how the world works!