I've come back from a fair number of games where I'm 20-25 life down, and I've lost a few where I was on the other side also. some mages are much more capable of this than others, but it all takes experience, playing for your outs, and playing to run a an opposing spellbook out of specific threats.
Seriously we need to start using chess clocks or something. That way people can spend different amount of time thinking in different rounds but they're still on a clock. The question is how much time to give each player. It's better than using an overall match time limit because that affects control more than it affects aggro.
No, we don't, but perhaps you do. You are welcome to say what you want/need in your games, but don't presume to speak for all of us.
I don't have ADHD, I LIKE long games, the longer the better and happily 16hr games of TI3. If MW runs to 3-4hrs I'm good with that, and would rather play one long game, than several shorter ones in the same time (that applies to any games).
Tournaments of all games need time limits. For casual play, that's down to what the players involved want.
it certainly is not fun for new players to get dumped into competitive scenarios, and as you mentioned, wait bored while they get destroyed in slow motion.
Again, that depends on the player. Competitive players like me thrive on that, and want it in every new game I learn. Early on in the learning curve, I'm happy to concede, and start another (and take advice on when you reach that point). With experience, I'll concede something truly unwinnable, but I enjoy the challenge of trying to bring it around.
I've had problems in introducing new players to the game, but it's honestly never been these. I suspect it depends what kind of players you introduce though - I don't think boardgamers are a good fit for example, and different kinds of gamers will present different challenges.