I absolutely agree. However, in my experience, recognition of the metagame comes way before you actually require it.
When I first started coaching LoL I came in to coach a team where the coaches I replaced suffered from some pretty serious delusions that come from the same place. They had very strong beliefs about playing 'the meta' and the value of certain flex picks at the time. When I took over and took the team back to fundamentals and reduced champion pools by half - winrates skyrocketed. It's really easy to want to copy what you see works for other people, but it's not always the best course of action.
I would say players around the border of silver and gold would benefit by paying attention to the meta.
And then there's players like BoxBox, who isn't exactly a one-trick, but clearly mains Riven. [1]He's at ladder rank 334 at the moment.
And as a final example, there's the monster himself, Apdo. [2]Apdo is a famous player in China who has on multiple occasions been rank 1 (or boosted people to rank 1...) using mostly Twisted Fate. He's more than talented enough to play any champion well, but is most known for TF. Similar to BoxBox and Riven, but on a whole different plane of skill.
All this is to say that there's no real need to change champions to continue climbing until you're at least above diamond, or if you want to play with a group where a synergistic team composition would be meaningful (like amateur tournaments).
[0]https://www.twitch.tv/cowsep
[1]https://na.op.gg/summoner/userName=boxbox