This is sort of true. I moved a wardrobe 3 times and by the third time is was kind of falling apart. But also it's pretty irrelevant because if it hadn't been IKEA furniture I wouldn't have been able to move it at all. Most furniture does not disassemble nearly as well as IKEA furniture.
But it sure would be nice if they used fewer one-or-two-time fixings like particle board screws.
You can buy packs of the screws etc. separately, though, and for a lot of the products you can also buy e.g. shelving, drawers and doors separately if anything breaks. At least I've always been able to do that in the IKEA's near me.
I don't see how extra screws would help - it's the wood that fails. And can you really buy spare parts? For example if you just need the side pieces for a bed can you buy those? I somehow doubt it. The "Spare Parts" page on their website is just an email form.
But it sure would be nice if they used fewer one-or-two-time fixings like particle board screws.