There's "incapable of working," and then there's "incapable of sustaining adequate employment." I agree that some people game the system. Some people are also trapped by it. Sometimes it's passed down through generations, where living off the government becomes a "norm," and I honestly believe that's a honeypot to be born into and hard to get out of. So is lack of education. And, to put it a bit harshly, so is lack of intelligence, in many cases. So is lack of transportation (need the money to get the car to get the job to get the money to get the car- etc). So is lack of job history- it's a problem that snowballs.
I see it every day- the cons gaming the system, as well as the people who will probably never be able to hold down a job. Sometimes, it's both at once. A lot of people in my generation especially have an unfortunate lack of grit and perseverance, which is a whole different rant and a whole different issue. I also see a lot of people who are only qualified for physical work, who are in their fifties and above, will not be able to complete a degree, will probably not be hired sustainable, will not even be able to stay on their feet all day. Physical jobs (including labor, but also just jobs where you're on your feet all day) have an earlier end point than desk jobs, and often the people who took those jobs in the first place end up least equipped to re-think their careers when they are no longer able to work.
What's someplace between depressing and infuriating is the plain and simple issue of what kinda of jobs do and don't exist any more. It's much harder than it used to be to just 'find a job.' Most sustainable jobs are high-skill now. Pensions are more and more a thing of the past. Lower-skill jobs that used to be for high school kids are now filled with workers across all ages- there's more competition to work in a damn grocery store nowadays than people even a decade ago would have believed possible. Wages aren't rising as fast as the cost of living is.
So, yeah, I see it as a complex issue, and not just an issue of "those lazy fucks."
There's also the issue of whether or not giving out disability regardless of need or merit ultimately costs society more or less than whatever would happen without disability. That's also a whole nother issue, but I know sometimes the stats on that kind of thing an be surprising. It's actually cheaper, for example, to provide a family with housing, than to lodge them in a homeless shelter.