It all comes down to how good the pool of reviewers is. I have no problem with an honestly run ARC service that adheres to Amazon TOS, but not every service manages to develop enough of a pool, and in some cases the reviewers don't take what they're doing very seriously.
I do ask myself if "This book was easy to read" will encourage people to buy my books. An awful lot of the solicited reviews through agencies that follow Amazon TOS are crap.
Some people sign up so they never have to pay for a book. That's why I have a library card, so I guess I can't fault them for wanting free books. But I do fault them for posting 25-word reviews that could apply to almost anything ever written.
I totally agree, but I have to say that a lot of my organic reviews read exactly the same way.
Rather than using examples from my books, I'll refer to a movie reviewer I've seen. He tends to do one or two sentence reviews, all of which that I've seen read something like "Garbage movie. Total waste of time." That's not useful to me, because I never know why he thought the movie was garbage. He is sometimes, right, but still...
The reality is that no matter how you obtain reviews, they will vary in quality. The bulk of them, both organic and otherwise, are probably not going to be that detailed. At least with an ethical review service, you'll end up with somewhat more of them.