Completetly understandable, I feel the same way. There is no build up with the girls, they all fall in love after speaking with them three times. While you have built a relationship with Katriona, Mida and your "family", all others just fall instantly.
The whole plot points of having mind control powers (my favourite ability in the game) while an evil mage is stuck in your head trying to corrupt you just ended quite abruptly, removing one storyline.
Everything that has happened has already happened. You have fought and absorbed devils, you have saved kingdoms, you have fucked girls etc etc. On that point, the recent encounters with Greed and Wrath were extremely dissapointing. No real buildup at all, you just find wrath after 15 minutes and Greed just approches you. There is no build-up to any of their fights, nothing feels dangerous, you don't even fight their henchmen. Greed had cool snake demons yet their designes were completely wasted.
Talking about completely wasted, your powers. Everything about them feels wasted. You can spawn servants of the devils you absorb, yet you neither train this ability, nor use it. You managed to summon the actual god of everything, and apart from your future, the rest of the questions were completely useless, another waste of a chance. The library is another such point. You have an entire library of informations and knowledge at your disposal. Questlines can be written about that alone, searching for ingrediences for some ritual, finding the meaning of runes, searching for artifacts written about, it just goes on and on, but the mc refuses this, no matter how much Cerea tells you to. Speaking of Cerea, where is her questline? Where is the controversy about her presence? Where is the internal struggle with the girls who have only experienced hardship by their hand? Everyone instantly accepts her after the initial chock, again destroying the chance for a good plotline.
The MC himself is also a big problem. Ignoring the previous reasons, the MC has absolutely no personality other than "joke with Katriona" and "being a classic stupid/horny mc". You got to make a select few personality choices in the first game, but they were ignored almost as soon as you picked them. One of the choices I remember distinctly is his view of other species. I made him into a human supremacist, yet I only got a comment about other species directly after making the choises and then he never mentioned it again. I chose to be with Mida for power, where is this ever mentioned? It doesn't even feel like your story is moving on. You never act differently, you never discuss or even think about future plans, rarely do we get to know what the other big players are doing, and when we do, so much time has passed that it's impossible to decipher what their plan is.
Every possibly interesting plot point seems to be watered down or even removed. I understand why you think it's gotten boring, I myself really don't feel like it's stayed remotely as good as it was or nearly as good as it could have been.
