At the end of the day, you pay peanuts and you get monkeys. Ok, that's actually a little harsh as there are some excellent flying club instructors out there. There are however, a fair few tits. I get £8.00 per flying hour to instruct. Admittedly I do it for fun and I'm fortunate that I fly for a decent living to pay the bills. There is no way on earth I could afford to do that full time. I have friends who do and they struggle. Seriously struggle.
The fact remains that you will almost never attract a decent standard of career instructor if that is all that schools/clubs are prepared to pay. I deliberately exclude the professional instructors at schools such as OATS and some of those who got into aviation at a later stage and are considered an unattractive proposition by the airlines (having said that, a middle-aged instructor friend has just been recruited for her first airline job).
If I were a full-time instructor at my current school, I would make approximately £15000 gross per year which would barely cover modest rent in the Home Counties, let alone a mortgage. Pension, what's that? Rest assured, I won't be instructing for a living as I wouldn't be able to stay in my current house (which isn't exactly Blenheim Palace anyway).
Sadly, anyone with talent follows the market and heads for the cash (airlines) at the first opportunity. Market forces. I appreciate there are always exceptions that prove the rule (usually with some other form of income) but there are a large number who remain who are either building hours for the airlines or are not suitable for them in the first place. That is not a basis for quality PPL instruction. Some of the suggestions already made would mitigate that. Bring back the BCPL maybe?
Ultimately though, I say again: Market Forces.