1) Selectively applying only for positions in companies where you truly care about the specifics of the role and the overall purpose of the company, because you want a specialised role and/or professional progression.
2) Indiscriminately applying for anything which vaguely seems like you might be able to do, even if it's not a good match and you care little about it.
I've not done a huge amount of interviewing, but last time I did so it was painfully obvious which categories the CVs fell into. All the (2) applicants were immediately rejected on the grounds of not meeting the required job criteria or were ranked much lower than the (1) candidates for not having relevant experience in the area or zero demonstrated interest in the area or specific position either on paper or in the interview.
You must tailor both the CV and cover letter to make a good impression. That's the careers advice I was given, and it's good advice. Not taking the time to do so makes it much more likely your application will be rejected outright, or be ranked below better applications. If your application doesn't demonstrate any clear interest or specific aptitude for the position, it's going to naturally make you appear less desirable than candidates with the same skills which do. The CV is selling you to the people reading it, and if no effort is made to market your skills and experience for the position on offer, then you're selling yourself short.
Last time I had to apply for a job, I spent a lot of time looking over job listings, and submitted four applications to four places, all tailored bar one. I got four interviews and three job offers. The hours spent tailoring each application paid off in terms of the response. And I got a job in a field I cared about, rather than something random. The one I didn't get an offer for was with Google, and that was mostly untailored because they weren't hiring for a specific role; I wouldn't have accepted an offer in any event, so no loss for that one!
I like my current job and I can't even remember what the job description said. Anyway maybe your technique works for your area and your skillset - but I'd fall flat on my face if I tried it here.
In the past, I have trawled through sites like Monster, Reed and other big generic sites, and generally been unsatisfied. I've had my share of generic and fairly boring positions from this route. You essentially have to take the best of all the rubbish that's on offer in an area that's practical to be. You're right that the descriptions are rubbish and next to useless, and I think in most cases this route should be avoided if at all possible.
But if you decide up front exactly which field you really want to work in, and then proactively look for companies working in that area which are hiring, or might be hiring, you can get something you really want and raise the chances of being hired as well. Particularly if you proactively reach out to groups which you want to work with; several people on my current team got hired after working for groups in other organisations doing related stuff--just being known helps, and being known to be doing good stuff helps even more.
FWIW, 2/3 jobs I've found on job hunt boards have been pretty good. I'm much more interested in what the team are like and the environment than I am the specific problem domain.
You are probably right that networking is better though. I read somewhere that the time to start networking is not when you want a job - that comes across as being needy. I'm trying to do it more now, at a time where I'm comfortable in my role. I'm hoping it works both ways - I'll also find talented people I'll be able to recommend to employers or work with.