You need to chill out and have some fun more, in responce to a couple of your points tho
Scout: Its still the new class, I don't have the bonk juice yet so I still play scout whenever I can, although I'll admit where theres already 2 or 3 scouts or if we're defending I'll try play something else.
Medic: I have to agree with most of what you put, but don't yell at bad medics too much, better to have a bad medic then no medic at all. Often you go on public servers and there isnt a single medic on the team. Also, stop comparing public play to matches. Matches are well run, well communicated affairs where everyone knows what they're doing. PUGs are full of randoms who don't know each other, might not even speak the same language, may have just got the game, or may be half blind.
Pyros: Yes they are best at spy checking, but others can to, and rather then sitting behind there turret, an engi can roam a little bit around the turret just keeping an eye on things, sniping with his pistol round the corner etc.
Spys: while you might call it stat padding or pissing about, camping near the enemy spawns lets spys selectively kill enemys (Such as engis and medics) before they even get near the front, this both instils a sence of paranoia and frustration in the enemy team, making them make mistakes. But spys shouldnt stay overly long, as soon as a few of the enemy have switched to pyro to hunt you down is the time to leave. Taking out snipers will often get them changing out and give ease of play to the rest of your own team.
Offencively spys can disrupt supply line by taking out teles, and this in turn takes the engis away from there precious sentry to go stick a new one down.
Engi: Yes, its better to get a higher level sentry up, but there is nothing wrong with a engi going and sticking his sentry down to start setting up, and leaving it to go get more materials or help out someone else. This is better management of time, while its in set up, you can;t upgrade it, so go get more materials, so when you're back its ready to put 200 straight into it to get straight to level 2.
Demo: Traps don't work as well as they did with the pyro pushback and bullets taking them out now, so only clever sticky traps, or suicidal/dumb enemies get caught in them. Yes the pipe launcher is much more gun and run, but a decent demo can use the stickies better then the pipe launcher, blowing them up in mid air aroud the target rather then miss iwth the pipe and do 0 damage.