You may be able to pirate it, but try to incorporate it into a new work and you're guaranteeing a lawsuit.

Even if you claim fair use?

Fair use exceptions are very limited in scope compared to what you may want to produce using the characters or other properties of a work.

Fair use is a defensive claim. You have to be willing to get sued if you want to invoke it. So invoking fair use is expensive and risky. Which sucks.

Like a small clip from a movie to use to teach people about something in a class or MOOC?

Like making your own Micky Mouse movie.

We have to do better in our legislation than "well, it's only a crime if somebody cares".

Otherwise, why bother having a law about copyright infringement at all?

You want people to be able to sue you even if you didn't cause them any harm whatsoever?

People are able to sue you even if you didn't cause them any harm. Regarding copyright, they'll even win (see "statutory damages", which aren't related to the actual damages).

Financial harm is still harm. You cant sue unless you are personal affected in some way, financial, emotional or otherwise.

Yes, financial harm is still harm, no argument there. But in copyright, the magic of "presumed harm" applies, so the plaintiff doesn't have to prove that they were actually harmed, hence statutory damages:

Statutory damages are a damage award in civil law, in which the amount awarded is stipulated within the statute rather than being calculated based on the degree of harm to the plaintiff.

You still must have been harmed in some way. You can't just sue and say "well somebody owns the copyright on that! You'd have to be the one to own it in order to sue. Continue reading about statutory damages and explains what they are intended for.

You must have your copyright infringed upon, that's not the same as being harmed. Hence why it's presumed harm - if the infringement itself counted as harm, there would be no need to presume it!

The Magnificent Seven might be a bad example there; it had a 2016 remake, which I'll bet led to some sales of the original film (and probably also the original original film, Seven Samurai).

Their estates for one. Also these media are still popular and still get restored/remastered/re-released so as long as they are profitable copyright holders will care.

Even if they aren't profitable or being sold copyright holders often try to prevent piracy anyway.