cylinder deactivation is the one can’t be improved on long-term reliability from any efforts due to the natural of design. Variable displacement automobile engine technology on cylinder deactivation simply doesn’t make sense for longevity.
Like someone else said, let it go and give the new owner a break. Let him enjoy the new ride.
As for your assertions and conclusions, there is no evidence yet that the 2018 Mazda cylinder deactivation technology is going to be a problem. No proof whatsoever.
You can't base your conclusions on something GM or Ford, or anyone else, did 10 years ago.
Same with the variable displacement and variable compression engines coming out. No history or proof (either way) that they will be a problem or a success.
Come back in ten years and talk about it then.