The correct way to assemble Ikea furniture is to apply wood glue (PVA or polyurethane) along every joint, in every screw hole, on every dowel, and along the edges of every backing board.

For extra points you can wipe polyurethane along any raw particle-board surfaces to seal them, like those on the bottom of a vertical unit.

It's about five minutes extra effort and $0.50 worth of glue for something like a large Billy bookcase.

This basically turns the entire piece into a single composite structure. It's incredibly durable. You cannot disassemble it to move but you can move it whole many, many times without anything breaking.

I have had to take a large sledgehammer to an Ikea entertainment center that I'd glued.

Walmart garbage does not respond the same way to this treatment. The Walmart (or Wayfair) particle board is a wooden oatmeal cookie. It crumbles from within regardless of how the joints are treated.