I'm anotherfag. I see, where you're coming from, and you're right in many regards. What you're saying about the shortened attention span is true, and posting on imageboards also can be seen as a surrogate activity. Just as social media is, or watching TV, listening to the radio, reading the newspaper, reading novels, and so on.
You may have noticed, that those other surrogate activities I've pointed out are much older than imageboards are, and in the past people came along, that uttered the same critique you're uttering here. I'm not saying, that you're wrong, but that people of all times and ages followed surrogate activities and wasted their time. I don't think, that specifically /pol/ imageboards are worse than what people did in the past, because /pol/ is scratching on taboos and also is spreading truths, people wouldn't find elsewhere. As a matter of fact, I think, that /pol/ may even be a surrogate activity in the enlightenment-sense instead of the timewasting-sense.
I can just talk about me personally here, but even though I agree with /pol/ on many topics, my worldview stems from sources, which require a little more attention than our memes and infographics do. But those memes and infographics often pointed me in the right direction. I also find it refreshing to have a larger number of dudes, which have similar views as I do, and do not care about the taboos the (((normal world))) imposes.
When it comes to lack of success in following some path to gain technical abilities and do something, you're also right and wrong. I'm one of the high-ability posters /pol/ has, meaning, that I released stuff into which I put a lot of work in, and which also required a lot of effort to learn the necessary skills in the first place. But I've also noticed what you said. People start some project, often highly motivated, and drop it two weeks later, never to be heard again.
But this also happens outside /pol/, and thingy may even be better on /pol/ than in the real world. I have a few skills, many young people want to have, because what I'm talking about is either extremely cool or would severely improve their lifes. I'm trying to teach them whereever I can. My usual experience is, that those youngsters at first want to learn, because it's cool and practical and so on, and after a few weeks stop, and do other things, often of some bullshit social nature, where they get their dopamine hits from.
In my opinion, /pol/ is less bad than what I know in real life, because on /pol/ you'll sometimes find some sudden outbursts of creativity, and people managing to create good things, even though their skills often are very shitty and limited, which is very positive, because everyone's skills are shitty, and it requires a lot of dedication to make something worthwhile out of shitty skills. I rarely find people with even this kind of dedication in the reality. In the best cases, people I know stop putting effort into something as soon as they reach some very low ability level, but they almost never refine their skills on their own.
In my opinion, school lobotomizes kids, and takes away their ability to learn in a self-sustaining manner. The constant dopamine hits of social networks also play a role, but even the real life of modern youths - which of course is largely centered around school - also consists of such constant striving for the next low-effort dopamine hit, and this already was the case before /pol/ and (((facebook))) even existed. If people learn something on a more professional level, this only happens, if you put them in some special environment where they're not allowed to do anything but learn what they're there for. Put them in their home, and the only thing they'll do on their own for a extended period of time is the bullshit dopamine-addicts do. It's school, and not even online activity.
What you're complaining about is a general problem in our world. It's frustrating, but it's everywhere. I also think, that this forceful lobotomization of every child born is among the cruelest things humans have ever done to other humans.