While you are putting together good evidence, he has a lot of experience on his side. As he pointed out, for some of your videos, people use different tactics. The game isn't straight rock, paper, scissors. Most of the situations you pointed out where a certain tactic (e.g. tilting pills) was bad, there were other reasons he pointed out which allowed him to be punished. As you demonstrated, you can win by avoiding the pills altogether. However, surely it is best to know all the options even if they aren't all perfect? Tilting a pill may be a bad idea is some situations, but in others, it will be the best option available.
However, sad as it if for you, Amsah goes out and wins stuff. I don't think you regularly place in international tournaments (correct me if I'm wrong). When Amsah, one of the best Sheiks in europe, plays the best peach in the world for a long period of time, you would hope that any positive things in the matchup would come up. Sadly, in PAL, Sheik really does get destroyed that badly. Hell, spamming Dsmash with Peach can cause you problems if you aren't careful. While for most people, it is winnable (possibly evenish in NSTC if Dthrow to Uair is as good as some make it out to be), the matchup should concern the top of the metagame. This means Peach at her best, not making mistakes.
Peach really does kill everything Sheik normally does well. No tech-chasing, chaingrabbing, not nearly as many combos, camping etc. Plus, a floating peach at the right levels with a turnip is a wall. While other top and high tiers have the tool sto deal with it, Sheik has a really hard time when everything that makes her good is gone.