Is total points really due to player activity alone?

[Eijolend]

You're right that it's technically not correct to say that activity is the only thing that determines points. But it's still the single most important factor once the system figures out what your skill rating is and from the number of points a player has it's NOT possible to draw a connection to how good the are.

As multiple people have already pointed out, it's possible to get a huge number of points by winning against a lot of fluffy players before getting paired up with better players and ranked properly. (Which is even worse than the point inflation imo)

The thing, what people mean when they "bluntantly state" that points are only made up by activity, is that once the underlying system has placed you correctly your ranking (and therefore your points) shouldn't change anymore because you win as much as you lose - but that's not the case, because there's this +6 or sth point injection thingy in place, so while your hidden skill ranking stays the same, the displayed points will increase over time with games won/played.

If you get better with time, you'll get a bit more points for a while, but you'll end up with the same amount of points as the other guy that is probably far worse but just played a lot. Although it might take you less games to reach that amount of points, your ranking is still worthless and no indication of your skill.

There are other factors as well that arise from this system. If you start 4 games and the matchmaking system is only able to find 3 opponents much lower than you which you beat, and one opponent a bit higher than you that you lose to. Assuming the skill ratings of the opponents are in a way that your rating stays the same, you'll get more points (3 wins) than if you played against 4 people with an equal skill as you and won half the games (2 wins). So even though your performance had the same worth (effect on skill rating), one case will give you more points than the other. So for this case you get more points because of how you were matched (i.e. who else was online at that time) and not because you did better.
I don't think that's a big issue though, since this should even out over time, but activity is still what we're left with.

The only relevant exceptions are people so far above or below the general skill curve, that the system just cannot figure out where to rank them and cannot find appropriate opponents, so the artificial boundaries of the system kick in. (afaik there is a minimum and maximum amount of points you can win/lose from one game) This lets highly ranked players increase their points at a much higher rate, because they get more points and lose less points than they should. (or vice versa for very low skill ratings)
But this applies only to very very few people, that constantly experience running into these boundaries. (I think p1noyboypj mentioned somewhere he only gets the minimum amount of points for most of his wins)

TLDR: Before the system properly determines your skill, points can vary by a lot of factors, which isn't really good in the first place.
After the system has found out your skill rating, your ranking points continue to increase because there are new points generated into the system for every game played. How much you get out of this is mostly based on activity, but also on the opponents you're matched with. If you get better over time, you'll get more points per game than someone who doesn't improve, but the effect on your points is small and indistinguishable from just playing more.
Your experience may vary if you're either very very very good or very very very bad, which is only an edge case.

If "It's based on activity!" is a reasonable way to summarize these things, is open for discussion - but I certainly think it's enough for someone just wanting to get a quick answer to their points mean. Especially since explaining the details doesn't really make the system sound any better.

And still the main problem stays: Points aren't meaningful at all.