When I first saw this topic in the "active topics" list, I was surprised to learn that it wasn't an old thread that had been recently reborn. As others have said, this is a topic that people have been discussing and writing about for decades!
Although I let my subscription lapse at Aikido Journal, I used to read pretty much everything by Stan Prannin. He's got a series of articles from the early '90s discussing this very topic! Specifically, he worries about collusion during techniques, a lack of weapons and hamni handachi work, weak attacks and poor follow-through with no resistance, and the poor fitness of many instructors -- not just in one, but in many articles.
This is probably the best example: "Realizing Aikido's Potential":
In yet other articles, Pranin is concerned that people have lost touch with the spiritual foundation of O'Sensei's art. I interpret that to mean that people think they're doing what O'Sensei said, but they're completely divorced from the entire context of O'Sensei's beliefs or the spiritual foundation of the art.
More recently, Ellis Amdur and Peter Goldsbury have written extensively on the same topics. I won't go into specifics here because there's a ton of writing and discussion with and from those gentlemen on this board.
My main point is that it is not just malcontents with "only' a decade of experience who are looking critically at aikido, its history, its assumptions, and its training methods.
I humbly suggest that aikido can very effective in a number of dangerous situations and
there are substantial systemic problems with how it is taught and the very common conceptions of the art.
I think there are some objective measures of how good one is at aikido:
1) Can I really hurt somebody if I punch him or her?
2) Can I take and keep my attacker's balance from the first instant?
3) Can I respond instantly and appropriately to force from any direction?
4) Can I apply a wide range of responses from crippling to gentle and choose
5) Am I moving in a totally coordinated way and generating power from my center?
Honestly, after ten years of training, my answer was no to most of these questions.