Ah, such innocence.

tl;dr "Don't Trust Anyone Over 30" White T Cotton T-Shirt (https://www.amazon.com/CafePress-Trust-Anyone-Cotton-T-Shirt...)

>>> And I can't help but think that it kind of make sense to me? Honestly if I'm still an employee by the time I'm 35/40, then I messed up somewhere.

Apparently, by your own logic, in a few years no company will hire you as an employee. In fact, you won't be hired because you're not a good "culture fit" (aka too old).

>>> Your memory certainly isn't going to improve with time, it can only get worst AFAIK, sames for the number of neurons, your brain elasticity, your capacity to learn new stuff. For instance I can honestly say that my dad learned less in the past 12 years than I learned in the past 12-24 months, even when he puts his mind to it just doesn't work that well anymore.

My memory is greatly enhanced with Google. But my understanding comes with time and experience. Lets suppose you work in robotics, such as with a spiffy new area like self-driving electric cars. Do you understand how to interpret a Lidar point cloud? I do. Do you understand SLAM? I do.
How about neural nets? I do. Up to speed on ROS? I am. Know how to handle the jerk derivative (no joke). I do. Can you compute the fourier transform of the vehicle dynamics? I can. Any clue about Denavit-Hartenberg matrix transformations? I have. How's your battery technology knowledge? Know the difference between NMC, NCA, and LFP? I do. How about the tradeoff of alternating current (AC) induction motors versus permanent-magnet direct current (DC) motors? Or perhaps knowing something about the tire composition for driving needs? What about autopilot... surely you know the neural nets and their interactions with the dynamics of the car. Do you know how use encryption to secure an over-the-air update? Do you know how to update the FPGA? Or even write a update for the car because you clearly know about the CAN bus protocol... I know these things. I'll admit it took me more than 12-24 months. Age has its limitations.

>>> In most cases you're going to be out of touch with young people(whether customers or employees), I think it's +/- inevitable and it's going to happen to me too at some point, that's just the circle of life.

Oh MY, a Lion King reference! SO 2019! Just what the 20-somethings are quoting on TikTok! Be sure to buy the T-shirt above.

Oh, yeah, and self-driving electric cars are SO yesterday. How could I be so out of touch? I should be in the Metaverse. I guess I need to get past my chapter 7 bookmark in Physically Based Rendering (https://www.pbrt.org/). That book, by the way, is an excellent example of Knuth's Literate Programming... but that was before your time.

>>> Now this may come off as really evil, but you're also more likely to get sick or hurt yourself. Do I want to have carpal tunnel syndrome or osteoarthritis from typing 8 hours a day for the last 40 years? Not really...

Lets see. I'm 68. I have been sick enough to stay in bed for a day once in the last 25 years. I type all day but don't have carpal tunnel. My neighbor is 40, has had back surgery and cannot work. My one friend had a stroke at 38 and cannot work. My 27 year old friend just got covid and seems to have lasting heart problems. My friend from high school died at 19. But I do wear glasses so I want a vision plan. Hey, old people are the problem.

>>> You've most likely got less stamina too.

Well, you got me there. I take naps frequently. But when I'm not napping I'm at my computer somewhere between 12 and 16 hours a day. Covid has had no effect on my lifestyle as I haven't been invited to parties or weddings for years. All I get now are funerals but they don't take much time.

>>> Statistically speaking you're less likely to change your mind on any subject, even if you want to, the older you get the more your beliefs are fixed, and the harder it is to change in any area. Not saying it's impossible, just harder.

I have a degree in Mathematics. I can tell that you haven't spent a lot of your 12-24 months learning anything about statistics. Yes, it is harder to change my mind but, since I study a lot, I can usually cite sources for my beliefs.

>>> Is there any non-emotional reason that causes people to think it's actually a bad thing?

Well, your wife and children might. Consider: Data from the BLS shows that approximately 20% of new businesses fail during the first two years of being open, 45% during the first five years, and 65% during the first 10 years. Only 25% of new businesses make it to 15 years or more. So if you go into business at 35 you have a 25% chance of being in business at 50.

Current lifetime statistics in the U.S. for males 75ish, females 80ish. Of course, that's only for sex. I have no idea what the statistics are for gender. I suspect that if your business fails when you are 50 you might "change your mind" about age-related discrimination. But that would contradict your previous point, so maybe not. Time will tell.

Now I will crawl back into my corner and scrape the Rust off my programming. Sigh.