'Perhaps I should just buy them all and read everything?'
That's EXACTLY the attitude they hope you will have.
I used to work for a company that published a few parenting magazines and the woman who sold ad space used to sit very near me.
The basic 'sell' was that first time parents were anxious and eager to gather information, and would spend a lot of money if they were sold to in the right way - in a trusted, supportive, premium environment. (This was in the days before the internet was widely used).
Parenting magazines provide a place to collect ad spend from products and brands targeting parents. The content is the hook, the enviroment is there to sell. they do make money from cover sales, but it's all about ads. As long as you know that, they can be enjoyable to flick through - but remember that they are all about parting you from your cash.
There are lots of good books you can buy/borrow from libvraries and all the MN advice is freely given!
So I prefer not to read the mags, just as I preferred not to buy wedding mags for the same reason.( the company used to sell one of those as well)
Working in mags doesn't half make you cynical.