Is 22-23 too young to be an e6?

Most definitely.

Not if you earned it.

Think about that. I didn't enlist until I was 25 as E-3. Made E-4 6 months later. Had I not went to the AF, how old would I have been if I stayed in and got promoted on schedule?

Too many variables to answer with an absolute yes or no, but I will say I did not possess the maturity at 23 to be a SSGT in the Marine Corps during my mostly peacetime years.
Back in 1945 when a SM may have multiple theater tours after 2 years in service, it would have been different.
In 1973 an 18 year old goes basically straight to Vietnam, comes home, reenlists, back to Vietnam a few more times and is an E6 at 22-23. I bet it happened.
In 2021, is a 22-23 year old SM with 3-4 tours in country mature enough to be a Platoon SGT? What about one in a technical MOS with only a few troops?
Bottom line, it can happen. If warranted and the individual is capable, it should happen.

I’ve known some surprisingly mature 23 year olds. I’ve also known some alarmingly immature 33 and 43 and 53 year olds. Perhaps suitability for promotion should be based more on technical qualification, experience, and personal character, and less on age.

Medal of Honor recipient, Audie Murphy, one of the most decorated Soldiers of World War II, was promoted to Staff Sergeant (E-6) in January 1944 at Age 18. Within months, he was the Platoon Sergeant, and by the end of October 1944 -- at age 19 -- Murphy was promoted to Second Lieutenant and served as a Platoon Leader. He later fought off a German company in January 1945 near Holtzwihr -- the action for which he received the MoH -- while still age 19.

Does that help answer your question?

https://en.wikipedia.org/wiki/Audie_Murphy#European_Theater

Age is irrelevant.

I joined the navy at age 17, then blazed through schools in record time. I made petty officer 1st class at age 22. I was ship's machinist and ship's welder on a nuclear submarine. I could repair anything, machine anything, and weld anything. Being an E6 means people came to me for advice, despite my age. But I sure got evil glares from gray-haired or bald old timers in the E6 mess ashore!

I was a 19 year old SGT. Then a 22 year old SSGT in the Marines. I was well prepared by that time. I had served as a squad leader, platoon sergeant, and platoon commander for a weapon platoon, and attended the SSGT academy. So yes with the proper preparation a young E-6 can get the job done!

I say both yes and no. Yes as sone 22-23 y.o are not mature enough to handle the responsibility that comes with the rank.
On the other hand, no. I have also seen abd know of 22-23 y.o. that are very mature for their age.I had a family member that was with the 82nd that was a SFC by the time he was 25. He had done three tours incountry in Vietnam and received field promotions. Di I think he was too young to be a SFC, no. He did a lot of growing up and maturing in Vietnam. He went on the make CSM and retired with 25 years active duty and suffers from his exposure to Agent Orange and PTSD.