It's a slow transition from bronze to challenger pretty much, but if you play matches a tier apart in mmr (e.g. due to swapping between a smurf and a main) it can certainly feel very different.
Still, by plat or diamond or so, most people are pretty mechanically decent, and know how the majority of champions work. While mechanics will still improve going upwards from gold, it gets into diminishing returns pretty quickly, and it's much more about decision making and teamwork that differentiates players rather than raw mechanics.
In bronze-gold on the other hand, it's not terribly surprising to encounter players who legitimately don't know what an enemy champs abilities do, and mechanics are very hit and miss. There are some players who are that low with 'ok' decision making but atrocious mechanics, and there are some players who have raw mechanics that are actually better than some plats but their decision making is awful (having gotten to their rank solely by mechanically outplaying their opponents).
Again though, it's all a slow transition and theres no suddenly jump from gold 1 to plat 5 or anything like that, and it's all pretty relative. Golds will make bronze players look like a bunch of monkeys, but diamonds will make the golds look like monkeys, and challengers would probably make diamonds look like monkeys. You can't really say anyone other than the challengers necessarily make 'good' decisions (and pro players might disagree), it's just as you inch upwards through the elo it's increasingly more likely that people will know the outcome of a given play before it actually happens, so you get less YOLO plays with people all in-ing only to lose as is remarkably common in low elos.