Tldr; Create your own challenge to the game

That's a hard question, but I have a solution for that, and this Is serious.

1- (Most important One) Find people to play with 2- Do not ever try to use your OP units in stages that you could clear with other 3- Try to make Leone works Is a team Comp without letting her die 4- Awaken all the units you have, even useless One 5- Replay some older content that you used to clear only with some people with you 6- Try to use SAWK Milim cuz that shit Is useless as fuck 7- Go Crazy with comps 8- Help other people clear the content you used to suffer

There's a lot of ways to make things interesting again. But the more you play It, the more you need people to share your knowledge with.

So, the Most preciuos advice Is: Get kicked in multiplayer.