I just saw it on another thread - 'mental health is rife thanks to covid!'. It's constantly used like this... 'He's got mental health!' 'They'll suffer from mental health if we don't open schools!' (this was a particular favourite as it reads exactly the opposite of what I assume the writer meant).
Everyone has mental health. They have since the beginning of time. It has not changed because of Covid or because of any other reason. It's like saying you have skin or internal organs or feet. Much like your skin or your feet, your mental health may be good, or it may be bad, or it may be somewhere in between. What you need to do when DESCRIBING mental health is to use adjectives, or even to say what you actually mean, with words like anxiety or depression or schizophrenia.
People will just say 'oh but you know what they mean when they use 'mental health' in that way - and fine, I guess? But turning mental health problems and illnesses into an amorphous and indistinct blob of generalised negativity doesn't give any path towards resolution or help.