That sounds like you are saying they should make level's easier so we can have stealth handed to us on a plate, and don't need M&E. I didn't NEED M&E, but I did like using it. Stealth was hard to achieve in SCC (without M&E especially), I liked that challenge.
You haven't played through Conviction without using M&E? What are you doing Frankie. There's so many ways to play SCC, not using M&E is really good and gets you closer to old school. 100% optional, Player choice.
I think Airstrikes will ALSO be 100% optional. Whether the levels are "designed" in a fashion that makes YOU 'need' the Airstrikes is on you brother. If they are optional, I will be able to make it through without them....cos I'm good at SC.
Er, Sam doesn't make mistakes? How's Lambert doing again? What about letting his Daughter get into a situation where she COULD have been killed? Sam makes lot's of mistakes, just like real World operatives. Fortunately he never made a mistake that cost his life, just little ones...that cost OTHER people their lives

Sam is not infallible.
You're right that Players make mistakes also, and just like you said, in Legacy it led to reload/twiddle your thumbs while waiting, and try again. In SCC you had were held ACCOUNTABLE for your errors and had to try and dig yourself out of the hole, in spite of the fact the mission could be considered a failure because you were detected.
And THEN, after completing the mission in an unworthy SC fashion, you could go back later and try again. Continually challenging yourself to make a clean Splinter Cell like, perfect run, rather than continually retrying a check point until you memorize all the requirements and perform them. That was more akin to being a rat in a maze than simulating a realish stealth operator, ON SITE experience, IMO.