Let's start off with a basic premise...it's impossible to achieve 100% perfect balance in any game. That much we can agree on. But here's the issue: it seems like Riot has completely given up on even putting in a smidgen of effort to get us close.
Instead they have adopted the "change for the sake of change" philosophy, with "everyone has their time to shine" being their primary tactic. To further explain. The change for the sake is their focus on changing things just to spice things up, targeting champs who haven't been playing in a while, or overhauls no one was asking for like the Runes reforged. It's a money grubbing tactic to just generate a general buzz and interest, while completely ignoring glaring issues and thing the fan base are asking for. It's 100% fanfare/smoke and mirrors.
Then they must have decided it's too tedious to try and continually balance the game. Instead they just gauge what people are talking most about and create a predetermined meta for that season. For instance, a couple seasons ago people complained about full damage comps and the snowballness of games. So the next season tanks and ardent censor supports with hypercarry ADC's are the flavor of the season. Then people bitched about that. What we saw come out next was heavy nerfs to team fighting cops with tanks and ADC's taking a hit. Then assassins and fighters getting a buff, crab got buffed, helping create this season's skirmish meta. Poke comps were highly viable in the middle seasons, but those got like, insanely nerfed into the ground. Just round and round, like a dog chasing it's tail. Literally 0 effort or intent to try and somehow make skirmishing comps, split push comps, poke comps, and front to back team fighting comps all viable at the same time. Here's the runb. At one time they DID do that. Go back and review worlds over every season, and there were several where the meta WAS that diverse. But at some point they just stopped trying.
The main problem is how insanely hard they gut the previous season's flavor of the month. You trying to tell me that Riot didn't know when they release Conqueror and nerfed ADC's, while also increasing gold income in the early game...that they didn't know already that front to back team fighting was gonna die and lane domination/skirmish meta was going to take over? Yeah right. I mean that's super easy to see just on paper, don't even need to see it play out. They need to stop trying to re-invent the wheel every season, and instead just continually tweak and adjust the game over time. And instead dedicate their resources to other fun stuff like new champs, skins, holiday events, etc. I would 100% rather have Riot spend like 95% of their dev and design resources on say creating a new champ or item, or releasing more holiday stuff for like all the holidays, rather than Runes Reforged or trying to completely reshape the meta.