Usage of the "too ... to" structure

I understand what you're trying to say without having to read your explanation, but grammatically it doesn't make much sense. If you didn't want to completely depart from your wording, an acceptable paraphrase could be:

"People aren't too old to learn but too lazy".

EDIT after your Edit: Both sentences are struggling to sound right because you're trying to define an action that has no subject. By saying "No People" you take away the subject of your sentence. Hence why starting the sentence as I did and adding the negative characteristic to the subject 'People' sounds better.