The gist of the criticism is that the AARP, which brands a variety of insurances, is acting in its own financial interest rather than in the best interest of its members. While it is reasonable to except a business to be in the business of making a profit, the AARP is supposed (or so the critics claim) to act for the best interest of its members rather than to be in the business of maximizing its profits.
Of course, the AARP has an obvious reply-while they are making profits, they also claim to be acting for the good of their members. This is, of course, a factual matter that can be sorted out by crunching the numbers (profits for the AARP relative to the benefits gained by the AARP members).
Of course, the AARP is not the only organization that presents itself as serving the interest of its members while also making a profit. While I am not yet old enough for the AARP, I do belong to the NEA. When I joined the faculty union in Florida, I also got a membership in this national organization.
Naturally, I had thought that the NEA was supposed to lobby and act in the interest of educators. However, I soon learned that the NEA was also in the credit card and insurance business. I regularly get junk mail (paid for by my dues, no doubt) pushing NEA credit cards and insurance. While I am for organizations providing benefits, it struck me as bit odd that my union was involved in such things. After all, my thought is that the NEA should be involved in doing what it is supposed to do and this does not include credit cards and insurance.
One obvious concern about such groups being involved in insurance and credit cards is that they now have a motive to make money and this can lead to a conflict of interest. After all, the NEA and AARP are (in theory) supposed to be acting in the interest of their members. However, if they are also in the business of pushing insurance, then this can be a bit of a conflict.