Any chance you could just deal with it? It's not the perfect situation by any means, but it's not unsquattable unless it's like BOSU ball-squishy. You can still get work done.
My current gym has mirrors on every wall, like most gyms. One of the squat racks is positioned directly in front of a weird seam were two mirror panes meet at a funky angle and totally screw with your depth perception. Kinda like looking into two mirrors that are side by side, while one is 6 inches closer to you than the other. It's not my favorite rack, but I use it if I have to. It's not the end of the world and isn't a workout-ruiner.
Anyhow, you can definitely complain to management, but I'm guessing they either won't care much or won't be able to make a change. Good quality commercial gym flooring can be expensive and a gigantic hassle to install (especially in an existing gym vs one without equipment in place), and they almost certainly won't just move the rack/rearrange the floor layout to accommodate you or others, even if you can convince other folks to voice an opinion.
If anything, instead of a wooden plank why not put down two 45s and stand on those. It'd be a bit more practical than storing a slab of wood in the corner of the gym and hoping no one throws it out, or carrying a 2x4 into the gym every leg day. Unless you're Jim Duggan, tough guy.