Smashboards

Then you're just gonna have characters with one-hit kill Final Smashes like Marth dominating Zelda anyway or characters with faster mobility like Pikachu getting to all the good items before Zelda does anyway.

Then the meta will develop, and we'll find counterplay. Any character can do fairly well with items, that's kind of the idea. It's gonna depend a lot on knowledge of how different items work, the best ways to use them, etc.

There's not exactly counterplay if it's randomized because RNG removes consistency. TAS speedrunners throw the randomness out the window by manipulating the luck by going back several frames to get the most optimal roll but you can't do that here because you don't get to decide anything. You can be in an optimal situation to finish off your opponent with a golden hammer, sure. However, yiu get absolutely no say in where the hammer drops, if the hammer squeaks or if your opponent randomly gets a Gust Bellows, so you can't recover.

I could say the same about Luigi getting a misfire that or Hero getting a critical forward smash at 0% with Psyche Up, or Peach pulling a Mr. Saturn, breaking her opponent's shield, and then pulling a Bob-omb to kill them at 0%. Of course there is randomness in the items meta, that's half the fun of playing with them. If you want to finish off you're opponent with a golden hammer, you might just have to decide if you want to take the risk of being launched offstage or having a squeaky hammer. It may be better to keep your opponent from using the hammer themselves and wait for a more reliable item, depending on the situaiton.