As already mentioned, you seem to gloss over a lot of general information before actually getting to the class itself and even then you're only really describing the scout rather than how to play him. Anyone who's opened up the game and played scout for 5 minutes knows how much health he has, what weapons he has and the fact that hit scan weapons can shoot through allies. But you also contradict yourself multiple times with your advice. You tell the player to stick with the team to increase survival even though he's a flanking class and you just told them to get around the enemy team to flank. You also say the scout is not a class for killing enemies, then go on to say that he can uniquely 2 shot 90% of players; that sounds like a class that should be killing people when ever they can.
What you really need to be talking about are scenarios where the class performs well and scenarios where he doesn't. Covering sentries as a primary threat was a good start, but don't forget that he also has specific tools to overcome his primary weaknesses. IE Bonk, If the player wishes to change their play style. Yes this isn't a primary load out weapon, but it's one of the first secondaries the scout will get.
Scout is a class of opportunity, just like the spy, the idea is to attack indirectly rather than head on, and prioritise "moments of maximum impact" over general combat. The same action executed at different times can mean the world of difference in critical moments. Attacking too soon just for a kill point gives away your position and puts the enemy team on high alert to future attempts of the same style. Although that's also not to say consistent harassment (such as of snipers) doesn't have its practical tactical advantages too if you notice a weakness in the team and are able to exploit that fact more than once.
At the end of the day each class performing well comes down to positioning and situational awareness. A scout in a large room with multiple obstacles is an ideal battleground choice, they can take cover and get the high ground very easily so you should encourage folk to pick their battles like this. Any position where a scout has to run at the enemy is a bad one and some maps are just overall bad for certain classes so players shouldn't force themselves to use Scout.
To play a scout is to play smart, you want to trick your opponent into thinking you're going to do one thing and do another. Then hit like a truck with that primary weapon. Know your enemy and their strengths and weaknesses. Soldeirs and demomen are good targets because they have low ammo counts and slow reloads. They're practically free points if they're not paying attention to you.
