I think the biggest problem is that there isn't much reason to keep playing unless you genuinely think you're going to win your next game. The system doesn't create much of a rewarding loop, so I think it's worth sacrificing a little competitive integrity to make the game more fun and encourage more people to play. More players ultimately means a more competitive game. Being the 10th-best player out of 20,000 players is more impressive than being the best out of 200, even if the actual placement is technically lower.

The current system also has very harsh swings early on. If you're a new player and don't know what you're doing, you can place very low, and then climbing back up becomes difficult. Even before climbing is actually difficult, you're scared to queue if you're tired or not feeling confident because losing puts you in an even worse position. That creates a situation where you think, "I'm probably going to lose, so why risk my ELO?"

I think some form of ELO protection would solve this. You don't necessarily need it at the highest levels, but at lower ELO, most people don't care that much about the exact rank. Someone in Slime 1 probably doesn't care whether they're in Slime 1 or Slime 2; what feels bad is being stuck and feeling like playing doesn't matter. Going from Slime 1 to Slime 2 feels good, while going backwards feels bad. That sense of progression is what makes people want to keep playing.

One way to do this would be through seasons. You could place lower than your actual ELO, then have wins give +1 extra ELO and losses give -1 extra ELO until you catch up. If you're actually a 50% win-rate player, you'll eventually climb. Someone who plays 100 games might end up slightly ahead of someone who plays 10 games at the same skill level, but they'll also start playing better opponents, so the inflation should naturally correct itself. Even over 1,000 games, you'd probably only end up slightly inflated because your win rate would eventually settle around 49% instead of 50%.

This creates situations where you can think, "I only have two ELO left to lose, so I'll queue anyway." Even if you're tired and don't think you'll win, there's little downside to playing, which is exactly what you want.

I also think the score should affect ELO slightly. Right now, if you're down 10-2, there isn't much reason to keep playing. You know you're almost certainly going to lose, so you might as well FF. But if playing it out could give you even a few extra ELO, there is at least some reason to keep trying.

I wouldn't make score matter too much, because then you could create situations where pace-baiting or forcing extra goals becomes optimal. However, I think there is a meaningful difference between losing 13-10 and losing 13-2. At 13-10, there were probably opportunities for a comeback: someone could make a mistake, snipe something, or get unlucky on a line they thought they could take. At 13-2, those opportunities were much more limited, so the larger loss should probably matter more.

There is also the concern that score-based ELO could encourage people to sacrifice safe wins for extra goals. For example, if you're up 11-2, you could play a safe Stronghold/End and guarantee the win, or you could go for goals and potentially let your opponent score a few more. But realistically, you're already so far ahead that you aren't likely to lose, and most people would probably choose the faster line anyway because nobody wants to go to the End if they don't have to. Even if the opponent gets a few extra points, you've still won.

I don't necessarily think all of this should apply at the top level. Guardian+ could have much stricter ELO rules, or potentially no ELO protection/score adjustment at all. At that level, competitive integrity matters more, whereas at lower ranks, making the game feel rewarding is probably more important.

Ultimately, I think the current system is too focused on competitive integrity at the expense of actually getting people to play. If people are constantly thinking, "I'm not sure I'll win, so I don't want to risk my ELO," they're just not going to queue.

I'm admittedly biased because a lot of these ideas are basically inspired by Valorant's ELO system, which people still complain about. But despite those complaints, people keep playing Valorant. The system creates a progression loop that makes people want to queue again.