First; I wanted to just nerd out a little with you, because the custom ladder you describe were the crucible of my gaming habits as well (geek cred, I think I even have some screenshots somewhere of when I was playing a Wintermaul clone with duke himself, from decades ago) :)
Second, I wanted to echo that there's a concerning parallel between paid vs free mods and free to play gaming. In both, I think the proposed solution _COULD_ be better. Some mods are ridiculous. (Skyrim on Morrowind? Some of the system shock 2 total overhauls?) I would _love_ easy, consistent, and safe channels to compensate the authors, and some sort of paid system seems fair in that sense. Similarly, if a game can be released free and keep passive costs going through balanced means (Path of Exile comes to mind) you CAN walk the line of "ethical microtransactions" or whatever the hell you call it nowadays.
But it's SO EASY now to point out failures in the f2p model, games that just gave up any attempt at legitimacy to pursue profit (which can be far more... subversive, in a f2p environment as opposed to selling traditional games, e.g. zynga). The worst part to this, to me, is that it's becoming the norm, as you say. People "are OK with it", and it eventually becomes accepted practice, and games that were once pillars of buy to play (guild wars 1 comes to mind) have sequels that essentially let you whip out a credit card for most of the end game gear, and fans who will _FIGHT_ you if you suggest this in any way moves towards "bad f2p".
I see a lot of potential for the cornucopia of modding creativity and availability we saw to fade in preference for monitization, and the true impact of this may not be seen for decades. (Is there really a difference in gamers who grow up being inspired by and playing with the hilariously accessible mods all over the place, and those who just play box products, or mods blackboxed so they behave as such? Selfishly, I can't but think so.)