I don't know about your specific case but it's typically not the presence old technologies that devalue a resume; it's their presence AND the lack of new technologies that does that, because it indicates that the candidate doesn't think it's important to keep himself up to date regarding the latest developments in his profession, which is a huge red flag.

Just this week we've interviewed a lady for a development position who had a very long career and had experience with not just old technologies such as, I don't know, Delphi, but she taught herself new things as well such as ASP.NET MVC and Node. She is a mother of two yet she has managed to find time to keep her skills up-to-date. Obviously we have offered her a senior position pretty much immediately.

The problem is that there's 100 new things, and it's hard to tell what's going to last and what's just a fad.

Also, once you have a job using X, there isn't much opportunity to get work experience in Y.

I've also have several recruiters say "Learning stuff on your own doesn't count. You need actual work experience in Y for employers to value it." That's hard when you have a job where they only use (somewhat-obsolete) X.

If they had to choose between you and somebody with no programming experience, who do you think they would hire? If they hired you both, do you think you'd get the same salary?

Answers are obv: (1) you (2) no - so your skills are not valued at $0.

I've had several recruiters say they'd rather hire a recent college grad than me, even for the same salary, because I didn't have experience in their specific technologies and it'd be easier for the recent grad to learn.

So I'm less attractive than a recent grad with no experience, which means my experience has negative value.

Actually, it's a win-win situation. Do you see yourself working at a company where most/all your colleges were hired, not because their experience, but because their age?

He is actually doing you a favor (in general terms, since one need food on the table...), and also protecting his company from frustrated employees (like you would, probably, be), since the young guys are able to endure more BS and bad management.

When I see one clueless hiring manager or recruiter, I can easily shrug it off and move on. When I see everyone making the exact same bad decision (your experience is worth zero/negative unless it's exactly the tools we need), then I wonder if I picked the wrong career.

Fortunately, I only need one job, so if 99% of people doing hiring are clueless, I only need to find one who values my experience and ability.

Your age has negative value, not your experience. If that new grad were the same age as you, that wouldn't apply.

Recruiters don't know shit

But they are the gatekeepers for getting interviews and jobs. What does it say for the industry when most of the people who are evaluating candidates are computer illiterate?

That leads to stupid stuff like when someone is hiring for MS SQL Server 2014, and they say that experience in MS SQL 2000 or 2008 is worthless.

Hackathons are a good way to make yourself try to build something in a short space of time with a new language which can teach you more about it than any amount of lessons.