I'm down with there being this reward system for KL because a bit of exclusivity adds some value to the cosmetics. I also like the ranking system for unlocking more items alongside the basic quests.
I do feel, however, that all of the above means very little when KL is inherently flawed in so many ridiculous ways. Shit encourages ignoring the league until everyone else has put in a ton of work to rank up with garbage point values of 10, 20, 25, or 50 while you get 100 or 150 points for beating them (and they lose 100). There NEEDS to be some sort of system in place that keeps people at lower ranks from cannibalizing high rank players' points at such an insane amount.
That too is why I have issues with it, the bad ranking system itself as some others have brought up when you're about to rank up to the next level it tends to match you up with players with high risk, low reward points wise and then likes to match you up with someone a few levels higher than you where they're like "oh win this and get 150 points, lose 50 though vs. someone you probably won't beat most of the time. I also hate and this has happened to me a few times including today, where it disconnects the players or freezes flat out, and then you go back to the ranking search screen and you lost points and rank. To me that's the biggest load of bs. The system desyncs me or I get disconnected due to a bad connection and I lose points? lol. Besides your examples of course lol.
The reward thing, I'd be fine with it if the game allowed the player to unlock such via other methods. They want to do even say a Gauntlet 2 for KL skins, gear etc I'd be down with that because that shit was hard af lol. I did the gauntlet but I bet you most players haven't or don't want to be bothered with that, it's very grindy but instead of facing human bs online, you're dealing with A.I. bs lol. I'm glad I legit got LK's Thunder Fire God skin from that mode but it was not worth it imo, they should have given us like 10+ skins not just a few. You have to use the right konsumables and assists otherwise you'll be there all day.