All that would happen much of the time is that people stop writing anything of consequence down, or seek secret channels like the WhatsApp example. NHS employees in the UK as another example admit privately all the time to not recording things in meetings to avoid FoI exposure.

I agree with you in principle, but you are fighting human nature in practice - generally no one wants to look bad in public. I think FoI legislation is important, but in practice the results have often been mixed, and the approach probably needs to be nuanced.