Two factors, ignoring the sci-fi part of things.

First, depending on armor levels, a slashing/chopping/cutting attack can be directed at places other than center of mass and be very effective. This gives you reach that you just can't achieve while expecting to end a fight via thrusting. As a general thing, it's referred to as defanging the serpent. You attack the parts that either hold your opponent's weapon, or otherwise allow them to attack.

This means in practice that someone doing standard thrust attacks can be at a major disadvantage unless they are significantly faster than their enemy.

Second, even if you don't defang the serpent, you can still attack the wrists, ankles, or arms from a better distance. You bleed the fucker out. This favors the kind of mobile, angular footwork you'll see in some forms of sword fighting. Lunges are necessary to close distance inside of reach. At some point, you limit yourself to a single angle of attack. Depending on your training and physical capabilities, a straight lunge is one of the easiest attacks to avoid and counter.

When it's done with something that can also slash, it decreases your exposure and allows for some really nasty feints for sure, but you've still largely committed to a movement. Committing like that can be good or bad, but if you're against someone that's countering you from angles you can't quickly pivot to, you end up in trouble.

Now, the argument for spears against swords is absolutely a good one. Reach is king in most fights, no matter the weapon or lack thereof. Mass is often queen, though I really dislike gendering ideas like this. It's just the frame of reference I was given back in the day, so it sticks in my head better.

But, spears are not the best 1 on 1 weapon, at least not the usual spear with a long shaft. The shorter spears like assegi are fucking beast mode, though generally are used with a shield, and thus hard to properly assess for a thrust vs slash kind of comparison. Plus, while I have fucked with spears, including short spears, I don't have anywhere near the actual sparring time in.

Anyway, point is that the point is at the end of a long stick. That length is a lever. When that spear is side by side with other spears and a shield wall, you're an idiot to run in with a sword.

But when that spear is alone? It's trivial to deflect and avoid. And I say trivial with the full meaning. It's absurdly easy. You run into some guys that train with kingfu type spears that can make it way less easy, but then again, that's not really the same weapon as you'd have if you taped a light saber to a big stick. They function in a different way than more rigid spears.

Now, let it be known that, despite the user name, I have nowhere near as much time in with swords. I did okay, I've trained and sparred, but I was always more of a knife guy. A lot of the same principles apply, but stabby stabby only in knife use is vastly inferior to using the entire weapon as needed. Trying to use something like a Fairbairn Sykes dagger against a bowie is not going to end well unless you're significantly better than the bowie guy. Different tools for different jobs, you dig?

Now, I agree that the on screen jedi moves are absurdly inefficient. There's people that have learned the stuff that was designed for the movies, and they get their asses handed to them if they try it sparring. Too many openings, too much wasted energy. None of it works unless you're using the kind of extra light performance sabers that are built for it. The balance of the weapons aren't right otherwise. Well, mostly. There's footage of some of those folks using aggression and mobility to do quite well, but it's still with unrealistic practice weapons.

But if you had an actual light saber, you'd stay tight, keep things close and do controlled slashes, more akin to what you see in kenjutsu. Mind you, most kenjutsu is two handed, not single, so there's only limited on screen stuff that makes for 1:1 comparison.

Honestly, Dooku is the most realistic swordsman in the prequels.