So what makes teenagers and people of the age grp 18-21 incapable of logical reasoning according to you?

I coach this age group and they are not incapable of logical reasoning. You are a different generation with different opportunities and challenges and some values are different. I believe that some of the differences are improvements and some are well, the opposite. It's tempting to question your logic if you disagree with me and to use my age as a weapon, but it's wiser to listen to you and first see what I can learn.

The only thing that is missing from that age group is the perspective of age. However, I've known many 18 to 21 year olds who exhibited good reasoning, and I've known many older people who exhibited poor reasoning, so logical reasoning skills aren't limited to any age group.

Younger people tend to be more passionate about issues they care about. It's certainly not limited to young people, but often young people are so on fire for a cause, they can't and don't want to listen to opposing points, and can become emotional.

I’ve been told here often that my opinions have less value because I’m 20 and that obviously means that I have no experience in life
Smh

Not incapable, but seldom taught any.
No matter the age, some people are born with a certian mind that lends itself to logic and reason more readily.
Life experience, is a great teacher if we let it be.
So, to think you already got it all figured out at 18-21 is illogical and not very reasonable.
Not all young people think that way, but some do.

Teens have different brain chemistry due to their hormones that makes them more irrational and spontaneous.

Not all,and not just that age group.

Age has nothing to do with the capacity for logic, reasoning, and common sense. It's learning how to properly analyze a situation and respond in a coherent fashion that's important.

I understand your question but I don't think I know the answer.

What I do know is that the problem is not limited to 18-21 yr olds.

I don't believe that all are... some, perhaps, but that can be said of anyone (But not te garden crocus!)

Oh logical reasoning they already have.
Practicalities of living, on the other hand...

I don't agree with that. Experience comes with age and skills can be learned but a smart young person beats a dumb older one.

People use ad hominen attacks when they run out of other things to say.

There is a part of the brain in frontal lobes that doesn’t fully developed until around the age of 25😊

The main reason to me is this person has not experienced as much of life as say myself. Hell I'm 68
Years old. I assume I have
experienced more of life, good N Bad, than someone of that age.

Lots of people assume age and experience/knowledge are directly proportional, in truth they're barely linked (if at all).

There are 16 years old guys that could beat my ass at the job I've had for 5+ years now, there are 40+ years olds who can't even wash their clothes or cook their meals (even extremely simple stuff), let alone think logically or take serious decision in any contexts/fields.

All scenarios are different, labelling an entire group of people is foolish.