I'm going to be honest: I think one of the ways you fix season 2 is by getting rid of Warwick
Act 2 was more or less entirely dedicated to Warwick, a new character who really isn't that new bc he's actually Vander from s1. Despite the fact that he plays a heavy role in the act, his character isn't explored at all. Warwick is used in act 2 for the main purpose of reuniting Jinx and Vi. The sisters end up basically ignoring all their problems and differences and become family again solely due to Warwick's presence. If you get rid of Warwick, then the sisters don't reunite. They either stay on opposing sides or they end up reconciling later in the show, most likely due to them developing some sort of understanding for the other and by actually exploring their baggage.
Warwick is tied to Singed in this season, and through him and Viktor he's tied to Ambessa. Half of the plot in act 2 is Ambessa trying to find Warwick by using Singed to turn Warwick into the ultimate weapon. This part of the show was kinda weird and it definitely took away from the plot. If you get rid of Warwick you can actually focus on ambessa and her motives, or on ambessa and Caitlyn since their relationship is established but not developed.
The sisters end up bringing Warwick to Viktor's commune, which is how Viktor gets reintroduced to the story after not being seen for several episodes. Viktor decides to attempt to heal Warwick, but it isn't said why. We learn that Viktor's powers are suffering and that the commune isn't all that it seems, but we never get to learn anything further bc this segment isn't focused on Viktor- it's focused on Warwick. If you get rid of Warwick, you could actually focus on Viktor, his powers, his commune, his relationship with sky and the hexcore, and his motives.
At the start of act 2, we see that Vi is in a really bad place. She's fighting a lot, getting wasted, and isn't taking care of herself. We see that she has a friendship with Loris as well. However, we're not able to explore Vi's friendship or her current situation or her character bc shortly after Jinx asks Vi to help her with Warwick. If Warwick is gone then you can actually focus on Vi as a character and unpack all the shit the show has built up.
At the start of act 2, we see there's a lot of unrest in zaun. We see zaunites starting to band together and view Jinx as a symbol. This is a really cool concept that isn't explored because instead of Jinx spending the act with other zaunites, she spends it with Warwick. If Warwick is gone then we could actually explore the current politics between zaun and piltover and the effects they have.
It really doesn't make sense to have Warwick be the center of the act when he's not a main character. Hell, he isn't a character at all. He's a plot device. Literally almost everything that happens in act 2 is somehow related to him, yet he has no arch in the season. Everything he does just adds to the plot, not to the value of the story. We end up getting the most random piece of lore dropped in the middle of the season because of him. Lore that literally wasn't relevant at all to what was going on in the show and was never brought up again. I understand that season 1 hinted at Warwick being Vander but if it were up to me I'd be prioritizing the other, much more important shit that s1 set up. Not fucking Warwick. Especially since he's just Vander, an excellent character that we were done with at the start of the first season. There's no reason for him to be back. Since act two is so centered on him, the other acts had to condense and become jammed packed full of shit. But if you get rid of Warwick, you give the story space to breathe. You could have things stretched out longer and in more detail because now you have the time to! You can go into the gray and Caitlyn's dictator arc in detail because now you don't have to worry about wrapping it up before Warwick shows up.
Warwick was literally so big in the show that he took away time and development from literally every character, but especially mel, jayce, ekko, heimerdinger, and Viktor, who were rarely seen this season despite being key players from season 1. If Warwick was gone, you could actually show what happened to ekko, Jayce, and heimerdinger before act 3. You could give ekko some much needed depth and screen time. You could actually explain the black rose, which is never explained throughout the entirety of the show. You could have had Ambessa's backstory be in the show and not its own separate music video. You could have showed Mel more. If Warwick was gone, you could actually explore the characters of Caitlyn and Vi and their relationship. You could explore Sevika's character, who got pushed to the side despite her promising start. You could explore Isha as a character. You could explore lest as a character, who was introduced and then completely forgotten. You could have expanded on the chem barons instead of glossing over them.
In general, if Warwick isn't around you just have more time to do more shit. Like holy shit this is actually crazy.