With sports like soccer it's quite noticeable that some people are way better than everyone else, or way worse. And there's no way to improve since you can't just rearrange thousands of teams.
For example in the Netherlands we have Football right. There's 9 divisions. You get promoted or demoted at the end of the season, such that on average you're roughly in the middle of a spectrum of 5% worse and 5% better teams.
Of course there's lots of individual differences and some teams get much better suddenly in one season, and ought to play a division higher right away. But that's an issue for online mechanics as well. Online mechanics make that 5% range more granular, sure, but the notion that thousands of teams aren't rearranged isn't true, that's exactly what happens in most sports!
Of course going to the court and playing a quick match with strangers doesn't have this effect, but the vast majority of football players play in some formal sense in a team which plays in some organisation's league system with divisions. At least that's how it is here, although football is an extraordinarily deep sport in most countries and so the difficulty of opposition will be less granular in other sports.
In the US we have baseball where we have a sane semi-pro system. In football and basketball which are the real money, growth sports, there's the best-in-the-world professionals, the unpaid 20 year old college players and not a lot in-between.
In college, a buddy of mine became close friends do with a semi-pro soccer player out of Austria. He wasn't the best in the world and he was an au pair in the off-season, but he was in tip top shape in his late 20s playing soccer for a living.
It really isn't like that here. On the top end of the average case scenario, you have 3 years to make a living doing what you've been trained practically 20 years to do and then you're out in most cases. The whole employment market for these athletes would be a lot more sane if it were like baseball where you have families coming out to see minor league football and basketball players at reasonable prices.
The people in those 9 divisions have a game every weekend, and training once or twice per week on weekday evenings, as a hobby. Pro sport is something different entirely.
I think competitive video gaming is like anything else, in order to excel and stay at the top you have to constantly compete against yourself.
About 2 months ago, I left my job at Facebook to move out here and it's been great -- I can always find someone that wants to play, and they're all in a good mood because they're on vacation.
As long as individuals recognize the limitations of their age groups they'll be just fine.
Actually, even if individuals _don't_ recognize their age limitations and play against 20-somethings that's also OK (if they're willing to have their ass handed to them on every competition).
BUT is is a dangerous game - you can get hurt playing against 20year olds!
My experience is that you need to play against people who will challenge you, but within an appropriate level of attainment. I am a keeper, so I will speak of keeper skills.
One important skill to learn early is to get off the line and cut off the angles. If you stay on the line when you are just learning, the net is too big and you have no chance to make saves.
Thus, you never learn to make saves because you have no real feedback on what you do. You always lose.
Now if you come out a bit, you start making some saves, and you get better at it. This would lead you to a place where you make nearly all the saves, and you would stop learning, unless your opponents are good enough to use passing and make you keep track of multiple strikers at once.
But if they are so good (or your defenders are so bad) that they are always swarming the net in threes and fours, you would get stick on the line and never learn anything.
So, the best way to learn is for your opponents to be better than you, but not so much better that they discourage good play on your part. And as you get better, they must get better as well, so that you must continue to get better.