I've been running Phandelver and Below but now realizing the added obelisk part is kinda mid. Now I don't know how to proceed

Hello everyone, I have found myself in a little bit of a pickle. So while I am not new to DMing this has been my longest running campaign so far. I started running Phandelver and Below for my party and they have just recently finished the Lost Mines part of the adventure which felt good because our first ever adventure as a party was through that adventure and we TPKd in wave echo.

This is not the issue, the issue comes in the form of the rest of the adventure, I had only given the parts after Lost Mines a few skims and the immediate parts felt cool with some tweaks I was making. However it falls apart entirely for me once they get to the collecting of the shards part.

All 3 dungeons with all 3 remaining shards are literally layered on top of each other. and the dungeons aren't very astounding either. then after those 3 dungeons you go to Ilithinoc and it continues to crumble with the briny maze and then the weird island hopping section before you get to the obelisk. and the final battle just feels underwhelming to me.

So I'm stuck with a choice. I have never written my own adventures before so just completely shifting away from it will be hard to do for me. I currently have the party going through a rewritten sunless citadel because I had venomfang flee there and one of my players backstories is connected to the dragon. I have another party member who is being hunted by the zhentarim for a debt and I have plans for Halia to be a villain in his side plot. I have another member of the party who has a vengenace for orcs after a clan with a feud for his family killed the remainder of his family. I was planning on rewriting the Sawplee goblins to be orcs to connect this story. And lastly which is the hardest to get around is I have a player who is a GOOlock and his powers come from an illithid tadpole that he got but is unaware of.

Basically I am looking for advice on ways I could rewrite the parts I have issues with or ways I can divert the story away with either other prewrittens or just suggestions from yall. Hopefully this post wasn't too ranty, Thank you in advanced for any helpful feedback!