It is very mature that you want perspectives and I appreciate people who are not afraid to say what they mean. You touch on a lot of hot topics here including agism, hackathons, "hacker" culture, brogrammers, and so on. I'll try to write a few replies to address your concerns.

I am one of these "older engineers" as you describe. Mostly I am well-respected by anyone who works with me because I tend to intimidate, but also be very helpful and mentor people. I do feel a lot of disrespect from younger people I meet in the industry. I actually look extremely young for my age, but I can hardly pass as a 22-year old.

Anyway, I'll start by discussing your generation stereotypically. I've been hiring people from universities for a few decades now and I am increasingly disappointed as time passes. Maybe I am just becoming a grouchy aging developer, my patience is wearing thin, or perhaps what I see is just reality. When I hire someone, especially out of school, I never expect them to know much about XYZ technology we use, ABC framework, or anything else I am using at the time. Simply, I look for smart people who I think my team can get along with in the workplace, are at least a tiny bit motivated to work, and are honest in every sense of the word. I learned the hard way it's better to hire someone who is a good, honest, hard worker than someone full of great ideas that can't execute or pisses everyone off each day. Unfortunately, I find myself disgusted by the type people who show up for interview and that I have to deal with from other companies. I do not ask for much.

Perhaps in the words of William S Burroughs, a few "words of advice for young people" are needed:

Do not turn on your cell phone during an interview, show up on time, do some basic research about us before you arrive, understand at least bullet item we wrote on the job description, etc. I'm not your dad and most definitely not your bro. Do not show up to the interview in your free give-away Angular.js t-shirt you got. That technology or framework you are named dropping and then trying to use to feign knowledge about? Well, you aren't fooling me, I probably used it or read about it, tried it, and realized that my instinct that it was garbage was true. I use more new technologies than you do because I am doing actual work as I have done for decades. Just because I am older than you doesn't mean I don't understand Ruby. Just because I don't seem impressed by your node.js github project doesn't mean I don't get it. More likely I am not impressed because your code is terrible and I am shocked that it took you so many weeks and commits to do what you would be expected to finish in 1 day at our office.

Remember that class where you decided the professor was as a-hole and that it was just too early in the morning to go to anyway? Was it called data structures 101? Well, it's going to bite you one day when you interview with me and you can't tell me when you would use a hash table and when you would use a list. Remember when you interviewed with me and you didn't get the job which you thought it was because I just didn't like JavaScript? Well, you are wrong, you did not get the job because you could not explain basics in JavaScript, your favorite language. Go ahead and criticize us for using Foo technology, because even though it's rock solid stable, works great in real-world production, and is making us millions, we were waiting for you to tell us to rip it out and replace it with Bar, which your buddy just put up on Github yesterday. But that's OK, because we're a lame company, and everything is our fault. We just need you to turn the ship around, so by all means, act like an idiot because there is no way we can live without your genius.

Do you want to impress me? Tell me what you know. Explain to me what will make you happy and motivated you. When you do not know something, admit it instead of trying to bs me. I hear enough bs from sales guys, marketing people, and VPs of the department of nothing to recognize bs before it leaves your lips. When you do not know something, do not give up. Tell me how you would do it differently or how you would go about finding the solution. If I give you hints or part of the solution, use it or even ask me for another hint. I am trying to help you because I am tired of interviewing people just like you. I want to hire you so I can get back to coding. I have already seen ten of you today, and I am currently considering offering a 5 million bounty for the next person who can sit in that chair and have even 20% of what we need to do the job.

You can be relaxed, just not too much. Most developers who have been at it for awhile really need to stay relaxed and do not take everything too seriously. You can have fun with us and talk to us. That does not give you a license to fool around, act unprofessional, or like an idiot. This is a job, and it takes very little else but hard work like any other job. Things are done by doing, not talking. People worth impressing are impressed by actions, not words.

/rant