You are correct. Other things also weaken the opponients team down. But as I stated, Salamence can do it much easier and (argubly) better.Your very method for dealing with Mence reflects how dangerous it is. Something like Infernape cannot switch in anywhere near as much times as Salamence can. Sure, Salamence has a SR weakness on the other hand Salamence has an immunity to one of the most popular moves on the game. With Infernape, its not so threatning that I need to sac the pokemon thats in against it to get a free switch against it. According to you however, you can quite happily throw away Skamory (or whatever ese is in at the time) just to get a free switch.
Ok, stop right there. Because you are already misperceiving the strategy.
In the example video, I did not leave skarmory in because I'd be willing to leave anything in on Salamence. That is a bad misconception. For instance, I'd never leave Flygon (my key to winning almost every game) in on anything it couldn't beat outright. In this battle,
it just so happened that my least necessary pokemon was out at the time Salamence came in. But! Neither is my strategy as simple as throwing out my least valuable pokemon to sacrifice to Salamence-- that's not the point either.
What I am doing is
NOT sacrificing, but making a smart move that also takes into account potential damage risk to my team (in this case, making a strong move against the enemy while keeping in mind the POSSIBLE risk of losing skarmory).
After all, it's always possible he'll DD up and let me blow him out. I'm prepared for either situation.
In short, it's more complicated. It requires a brain to play this game.
When facing a powerful sweeper, and this goes not only for salamence, but against pretty much ANY difficult switch in, there are not 1, but 2 main factors and a bunch of minor factors that go into the decision. The two main factors are:
A) Initial Prediction of the incoming move
B) Evaluation of risk to the team
These are the two immediate factors that come to mind whenever facing a difficult switch-- or in fact, facing any turn in the game when thinking from a defensive perspective.
A is where the prediction occurs-- what you think Salamence is going to do next. However, A is gambling, because it is not knowledge, it's a guess.
B however, is real knowledge. You know what the risks are to your team, and you know exactly the most deadly possible outcomes for your team-- so you can rely on B as real basis for influencing decisions.
However, it's the culmination of A and B that gives you your final decision. In the decision facing Skarmory v. Salamence, I might initially predict that Fire Blast is coming, but evaluate that leaving skarmory in poses the least threat to my team, and decide to stay in. Or, if I'm REALLY REALLY certain fire blast is coming, I might switch even if the possible damage to my team from a mis-predict is higher.
It all depends.
The point is that you play the game making decisions that take both potential risk and prediction into account. Also keep in mind that playing while assessing potential risk means that you also consider back up plans. You know will happen if you mispredict and how to turn it around if necessary. You don't make the move until you consider what could be happening on the turn after that.
If this were a game like Go and Chess I would be more understanding about having issues predicting the enemy moves, but in Pokemon there are only 4 possible scenarios (at best) from the enemy side, so it's easy enough to imagine the possible positions on the next turn.
On the offensive side, Salamence can only try to predict what you will be switching in and trying to hit you with the right move (or DD at the propper time). But the risks of not going for the obvious fire blast on the skarm in front of it is high, and it is harder for it to throw out move Y (usually d-meteor) just because it represents the most potential damage to the enemy team.
Defensively speaking, you are better able to set yourself up for the next turn based on B assessment, or make a play to base a turn on A while having a back up plan via more assessment. There's more flexibility on the defensive side. Salamence has only 4 attacks, but you have multiple pokemon to switch to, or stay in and use a number of different moves yourself.
If you play smart on both assessing risk (and yes being aware that risk IS present and SHOULD be in this game) and making your predictions, Salamence becomes much less scary.