I had to go to IKEA for some furniture during a hotter period in the summer. The amount of people just hanging out and preventing us from actually trying the sofas was really annoying. So yeah, you can do it but it's a bit of a dick move to actual shoppers.
(also fuck IKEA for making their store into a huge maze where you almost have to go through the entire thing even if you just want a single item)
I've only ever been to one IKEA, but at least for that one, there were somewhat subtle but definitely visible holes in the walls and displays to allow you to cut through the maze.
ETA: Also - again, for that one - if you know what particular item you want, you can find that item's location on the website and go straight to the warehouse to grab the item off the shelves.