If you let me, I will give the same piece of advice, though with a very different argument to justify it.
What is Riot Game's first concern?
Is it their players? They push buffs or nerfs that make no sense for commoners, e.g. bringing Sejuani down a notch when she already isn't in the best of states; they increase unavoidable champion damage (Darius' W damage, Kha'Zix' passive damage) after admitting that damage overall was a little over what it should be for the game to be healthy; they deem watching more important than playing, as highlighted in the last patch notes; during the PAX event outrage, they let all Riot employees know that they were to ignore players entirely, as they usually do anyway. If players were Riot Games' first concern, they surely wouldn't do such things.
Is it their viewers, then? Tickets for worlds championship are bought by bots within a few seconds of their becoming available to be sold again at much, much higher prices, and it has been a problem for years, support says. If Riot Games cared for their viewers more than anything else, they would have implemented any of the simple ways to prevent such a thing from happening.
Their professional players are too few to be any real concern, and balance changes around them are once again turned towards watching, not playing; their employees seem to suffer the same kinds of problems people in other large companies do, Kotaku says. We can reasonably assume that people aren't Riot Games' first concern.
So let's see what Riot Games has done these last few months: they buffed Kah'Zix right before announcing he would get a skin, as they did with some other champions; regarding skins, they release the most of them for the most popular champions (Ahri for example), almost none for the less popular ones; they're selling a "worlds pass" that costs no less than €15 in EUW and is pushed onto players with this sneaky "claim tokens" button on the mission tab, as if it were only one click away (might also add that it doesn't contribute to the championship prize pool; it's all for Riot Games); said pass grants you tokens based on the number of games you play, and some rewards require intense grinding (prestige skin is 2,500 tokens, you earn 10 tokens per win in SR if you score A or higher; that's 250 perfect games, over 100 hours of play if you're Deepmind, twice that if you're just human), which in turn boosts games played by this much (they'll then say that theirs is the most popular online game); some "missions" require you watch games on their website, which boosts viewer count in a fraudulent way because you're no "real" viewer if you do so to obtain a reward; they don't care who buys worlds tickets as long as they're bought.
The common point of all these statements is that they involve money. Buffing a champion so that it is wholly over the top makes more people play them, and more players are more opportunities to sell a skin, especially if it's brand new and glorious; the worlds pass could have been optional, but if you want even 10% of the event stuff you have to buy it; the way they try to sell it is just dirty tactics; if they have more games played per month, they're more valuable as a company; same if they have more viewers; etc.
Riot Games' first concern is money, especially when they lost 21% revenue over one year.
With that in mind, what is left for any player to make themself heard? First they should, indeed, tell the company that they don't agree with the way they do things.
Now imagine that you're a grocer and you sell banana chips, and I'm a customer who really likes banana chips. Every day I come to your shop, I complain about how your products are expensive, and your shop looks bad, and the chips aren't even so good to begin with, and the way you advertise your products is dishonest; and I still buy the banana chips because you're the only one selling these particular chips in the whole town. Every single day, I voice my criticism and still buy your chips, and this has been going on for months.
So tell me, would you renovate your shop? It would cost money and I wouldn't buy more chips, because I already buy as much as I need every day.
Would you change the way you advertise your products? It brings people to your shop, these people give you money for your products, there's no reason to change.
Would you change chips to sell more tasteful ones, or decrease prices overall so I don't feel ripped off every time I buy? I'm buying the chips anyway, and decreasing prices would mean losing money.
I could go on, but in short: most people wouldn't, because as long as they're earning money and it is their sole concern, then they won't change a thing. You don't fix what's not broken, and you don't change what works. You could call it "blatant disdain" and I wouldn't disagree.
So what's your role in that?
If you like banana chips, whatever criticism you voice, if you still buy my chips your qualms are well-heard but ignored, because they have no impact on my business.
If you threaten to stop buying banana chips because they're too expensive, I might raise an eyebrow and tell you that you can indeed try and find some in another shop, knowing very well I'm the only one selling those in a 50km radius.
If you actually stop buying chips, then I'll think you'll back soon, or maybe you really won't buy any more and you're just one customer in hundreds.
If tens of customers voice the same complaints and stop buying after letting me know they would indeed stop, then I might see my revenue go down a fair bit. If I was planning on hiring another employee to take some time off, then I might need to postpone it because I'll lack the money I thought I would have.
Most importantly, I'll know that if I don't do anything to make my shop look better, or if I don't decrease my prices a bit etc., these customers won't come back, and I might even lose some more.
Riot Games is only one kind of grocer, and you're one kind of customer. If you stop buying for the reasons you complain about, then you will add to their loss in revenues. And if numerous people do the same, then even Riot Games will have to mend their ways, otherwise they'll go bankrupt, however much they pay their marketing team.
The idea isn't to stop playing, or stop complaining, or any combination of the two: it is to stop giving money to Riot, entirely or in part, until they realise that your opinion matters. Next time you see something that you really want to add to your collection, ask yourself whether you can stand doing so while Riot Games isn't trying to make you joyous by offering quality content, but to fill their pockets with your money, whatever complaints you voice. Next time you hear of someone likely to send you a skin as a gift, tell them you don't support Riot Games' policy and would prefer they buy you a novel for example, or a film, an album of a band you like.
It isn't much, but if every player cuts their spending by even 20%, Riot will see their revenues drop some more, and they might feel entitled to act.
Because buying is, in a number of ways, supporting; if you don't support, don't buy, or buy less, otherwise nothing will change.
Hope that makes more sense to you!