Ehhhhh as someone who has been playing since season 1, runes/masteries/runes reforged have always been my least favorite aspect of the entire game. Even when runes were just stats, people minmaxed for their character then Riot nerfed the character so basically their "base statline" was including runes and if you tried to think outside the box you were playing suboptimally. Basically free to play players got stealth screwed over because you wouldn't think runes are as important as they are but level 1 they are disproportionately important and that snowballed people with full pages into a lead.
Certain masteries over the years, even before keystones, also dictated the meta to an extent. And like with runes, if masteries weren't wacky and noticeable they basically were just added to base stats and became boring.
I think runes reforged was interesting for a couple months, and there are some good ideas in there. Practically the whole Inspiration tree is super cool and quirky without being over the top OP, but as we know people don't care about Inspiration 99% of the time and all the damage and lane sustain stuff is what people spec into and now stuff like Electrocute, Fleet Footwork, Conqueror, etc. is just a base part of a champion's kit to the point where it's hardly distinguishable to see what choices people made, like before.
Basically what I'm saying is if literally all the scaling was done in game with levels and items, I personally think the game would be in a better place. There can be no assassin without a damage rune because their bases were knocked down to accommodate runes, there can be no tanks without Aftershock (usually) because damage creep from runes has essentially made a "normal" tank without insane surviveability on initiation nonexistant, and there can be no enchanters without one of the shield runes because their shields were annihilated last midseason.
TL;DR is that runes, after people optimize them, become a base part of a champion's stats and are no longer exciting or even really a choice as a result. Basically the only choices people have for runes are juggernauts deciding if they want Grasp or Conqueror, and certain mid mages choosing between damage or Glacial augment builds.