I used to think that the word criticism automatically meant a negative pronouncement, when in fact it can mean assessment that is either positive or negative

Yes, timely reminders of true meanings, Jackie & Bill.

Only problem is where the true meanings have been supplanted by excessive usage in (for instance) a negative context.

It's a bit like decimate, where the commonly-accepted meaning (and usage) is sigificantly different to the true meaning of "reduce by a tenth". These days (over the last 10 years) the original meaning has been relegated to a second-rate alternative in most dictionaries.