I would say that you are basing your view of Aikido on a select group of practitioners without the advantage of understanding. What type of people are you observing in practice, are they avid martial artist types...dojo dogs, there whenever the door is open? Or are they simply looking at Aikido in terms of recreation or exercise. Are thier instructors also sloppy and "weak" appearing? If so that could be the root of the problem, as bad instructions creates bad students.
I have often seen college kids walking to Jeet Kune Do classes on campus...they couldn't begin to stand up to a real attack (I seriously doubt that many 'practitioners', myself included, could), but does that mean that Jeet Kune Do is ineffective and weak? Not at all, just that the representatives of the system that I have observed are.
There is really no true standard of 'measuring' a martial art of philosophy, as it transcends the abilities of it's students. I honestly believe that Aikido is the perfect martial art, which makes it that much harder on it's students as they try to learn it. It demands a 'perfect' practitioner to do it justice.
I agree the the low intensity nature of many Aikido dojos invites atypical students (I was grossly overweight for an eleven year old when I started), but measuring the worthiness of any art by its followers is folly. In that case Christianity would be viewed as the sum of the worst hypocrites, the Hippocratic Oath seen as the pledge of med school washouts, and Universities rated by the lowest student GPA's.
I'm sure that there are a lot of inneffective karateka and kickboxers, (especially now that 'cardio' kickboxing is in vogue) but a generalization of Aikido based on a few observations is worthless and shortsighted.