Its not an excuse for screwing up and you are smart enough to know that.
His age is not the point in the least. It is about the # of snaps and reps conducted as a full-time high-level football player.
For his entire HS career he was a football and track guy. Same thing at Miami. So that means no spring practices, drills, and scrimmages. It means far less reps and position specific coaching than comparable players in other major NCAA programs that only play football.
2017 was Burns' only year as a full-time football player.
Now, the pessimists and grumps on here look at Burns see the 1st round draft cost and ONLY acknowledge the mental mistakes, technique issues, and lack of physicality. That's fine, everyone is entitled to their opinion.
Others of us choose (again - only an opinion) to look at Burns and see a young, raw, still developing player who has some serious holes in his game but
projects to be Ike Taylor - tacking + catching INTS = borderline Pro Bowl CB.
Ike Taylor was a similarly raw CB prospect coming out of school and he didn't play a full slate of games until his 3rd year. Burns started and played average at worst in his rookie year. Now, Burns was more developed coming out of school than Taylor, but that the point holds.
Here is the list of CBs drafted between 2015-2017 (
http://pfref.com/tiny/yilZw). There are about maybe a half dozen guys on there that I know are better than Burns and would've loved to see in a Steelers uniform (Peters, Ramsey, A. Jackson, Lattimore). All of them were drafted before the Steelers' pick in their draft year.
Burns is leaps and bounds better than any CB this team has suited up since Taylor hung 'em up. That's enough for me to be optimistic about his future development. Remember, even Rod Woodson didn't start a full season of games until his second year and didn't become the all-time destroyer of offenses until his 3rd year. Is Burns even in that same ball-park? Absolutely not - but I refuse to understand why anyone can look at a woefully inexperienced player in his second NFL season and say "Well, yup. That's his ceiling. No way he gets better. Next!"
If Burns is a motivated worker and smart enough to take coaching -- he can be Ike Taylor+. Is Burns that guy? Or is he a knucklehead? I have no idea. I don't know anything about him. Time will tell.