In a word? Yes.

It didnt mean that all existing battleships had no military value, but that Dreadnought could easily defeat any single one of them, and really likely a few at a time. And those it didnt wish to fight it could out run.

It mostly comes down to the number of improvements that were embodied in the hull of Dreadnought, focused in the areas of her protection, armaments, and propulsion.

First off, while not a huge leaps, she did have a thicker main armor belt than say the preceding King Edward VII class BB's. Coupled also with a larger ship it provided much more reserve buoyancy, meaning that the ship could get a few more holes poked into it without sinking.

Then we have the 5 turrets mounting a pair of 12 inch guns each that made up her main battery. Previous classes would have just a pair of 12in turrets, then a mixed battery or some maybe 9in guns, then a step down to 6in, and a dozen or more light quick firing guns. This made fire control hell for spotting purposes when everything was going, and of course it meant that your guns could only engage as the range closed enough. And while lighter guns could ravage smaller ships, or the exposed portions of a ship and crew or superstructure, it still required closing the distance. And in the time that took a single 12in hit could destroy an enemy ship, or bring incredible destruction like the Russian fleet found out at Tsushima. And while mixed batteries did have the advocates, in the US Alfred Thayer Mahan the famed theorist was one, Jackie Fisher among others were all aboard the uniform heavy main battery train. Dreadnought then would do away with everything but the 12in guns and a gaggle of very light exposed quick-firing mounts meant to ward of torpedo boat attacks that moved too fast and close for the main guns to track, and larger secondary guns would only progressively be added back in later classes.

And finally she was the first British battleship to be powered by turbines over older reciprocating, triple expansion engines. This along with a lengthened hull allowed her a remarkable for the time top speed of 21 knots, generally a good deal faster than existing capital ships.

It was the combination of elements that made her head and shoulders above everything else afloat.

Yes, quite so. The time around the turn of the 20th century saw several dramatic changes in naval warfare, but it took someone to realize all the implications and build a truly "next generation" warship for that to become startlingly apparent.

The traditional way that ships would engage one another was to come in close and exchange a huge volume of fire from all manner of guns. The thinking was that the more total weight you could throw toward the enemy the better. Through the 19th century canon transitioned from line of sight weapons to artillery that could hit targets miles away, even over the horizon. And naval guns made the change as well.

There's a huge problem here if you know what to look for. If you have a great diversity of naval artillery and you fire off a big salvo towards the enemy several miles away, what happens? Well, almost certainly you're going to miss. But each variant of gun on your ship is likely to miss in some slightly different way, and will need unique adjustments to bring it on target. How do you know which splash in the water corresponds to which gun? You don't. Worse. What happens when the enemy is outside the range of some of your guns, thus limiting your effective firepower?

For those reasons it began to make sense to concentrate on a standard big gun for a ship and having as many of them as possible. Thus the "all big gun" ship design. The advantage is that all of your firing solutions can be the same (ish) and if you see that your shots are landing too close or too far or ahead or behind you can make an adjustment to all the guns and be more certain of hitting the target. And by hitting the target with a full salvo at great range (the HMS Dreadnought dropped 10 rounds at a time) it's like a shotgun blast, you can spread out the shots because all you need is one to hit.

Perhaps just as importantly, concentrating on maximum firepower from big, long range guns meant increasing the effective engagement distance of your ship. Distance has always been the most effective defense, especially on the ocean, and that's a massive advantage a big gunned ship can have. It can engage and destroy targets beyond the range of their weapons.

Couple that with powering a ship via steam turbines, which increased speed and acceleration significantly, and you have a dramatic change in the naval battlefield. Ships that can outrun and outgun anything else out on the water. That doesn't mean that HMS Dreadnought would for certain sure win any 1:1 engagement on the ocean but it would have a massive advantage. The perception was that the Dreadnought would have a much higher chance of destroying any vessel it engaged with than the target would have of destroying it, and could thus continue to destroy enemy vessels by maintaining engagement ranges where it was much more effective, something it could do because it was faster than any other ship. For those reasons other naval forces perceived their vessels as unable to effectively engage with HMS Dreadnought and have any sort of reasonable chance of victory. That's obsolescence. And it's why other navies sprinted to keep up or keep ahead of the Dreadnought and its successors.