I don't have any particular gripe with instructors, I have never been comfortable with anyone looking over my shoulder whatever I am doing. It's just the way I am.
I do have an issue with the biennial flight requirement though. When I first got my NPPL(M) there was no need to do the hour flight, licence reval was done by a signature in your logbook, by an approved licence signer, who knew you well enough to know that the hours claimed were correct. This boiled down to buying a pint at the club meeting for a fellow pilot who flew with us on our annual trip touring France. The cost was less than a fiver. Then without doing a proper impact analysis someone who didn't represent microlighters decided to vote for a change of requirement. This now costs most of us £100 plus for the reval flight with the instructor. I would be interested to see whether it has brought any improvment in the accident stats. It is barking. The folk who still hold the old PPL(m) licence still do it by the pint in a pub method. Strangely, they have not all crashed and burned.