You want me to be honest? Most of these games including this one that involve NTR, they will have talk about a vanilla route but that's mostly bullshit (very few offer actual avoidable NTR). At the end or maybe in a couple more updates, Liz will probably fuck Matt. I could be wrong, could be one of those you constantly cockblock him and he never actually manages to get her BUT the fact that even on the 'Lover' Route her willpower constantly drops and she thinks about him at times makes me believe that at some point in time Liz fucks Matt and its one of those centered story points that effects how your character reacts and the ending you get. My opinion on how the routes will end.
NTR, Liz later dumps MC for Matt or forces him into cuck holding (MC might commit suicide or kill them); NTRS (though not fully implemented), you willingly share Liz with others and enjoy being semi-cucked; Happy, MC and Liz keep dating but she becomes Matts fuckbuddy without MC ever knowing; Lovers, Liz finally sleeps with Matt but you and her keep dating and move on.
If you follow NosyFellow on Pa. treon then you might know they also have plans and possible consequences for later Routes and the friends who have helped the MC from letting Matt fuck Liz. Not sure what they fully plan on but with the hidden chats you can buy on the Lovers Route it seems Matt needs to seduce and fuck Liz or suffers the consequences. If at no point can the MC get revenge for/toward Liz and Matt, then I'll consider it a complete flop. No way do you flip out over a POSSIBLE comic scene but after learning it happened and she wanted it to would the MC not go Ape-shit on either Liz or Matt.