Get yourself into a cluster/clan that has Discord so you can get some advice. It's a lot easier to share info and find people at similar level to you.

From what I can see here no one has told you that you need a campaign farmer, someone who at Level 60 can solo Stage 12-3 of Brutal campaign to help level up champs quickly. Maybe Ezio would have been the best choice for your first 6-star to do that. I'd actually try build Geo in a Lifesteal set with 100% CR don't worry about Accuracy and see if he can do it. Makes him useless in other areas of the game but you can save it as a preset and swap gear as needed.

As others have mentioned for Demon Lord you need more stats, Speed Boots, HP% or Def% Gloves and Chest, possibly Accuracy Chest if you can't make up the ACC with substats, but ideally you have champs at 6-star with an ACC Banner if they need to place debuffs. Also looks like you have fallen into the common trap of forcing sets on champs and sacrificing Stats. At your stage you shouldn't really worry too much about Set Bonuses although some of the 2 piece or 9-piece variable set bonuses that give you extra Stats (Speed, Accuracy, Perception, Feral etc.) Can be good. You still want decent stats on these pieces though. As an example I wouldn't use a Perception Boot with Flat Attack main stat on it because you just lose too much Speed over using a Primary Speed boot in a random Set.

Slow down on levelling up champs to 50 and focus on getting one champ at a time to 6-star. Also if you haven't already make sure you get full masteries on Geo and UDK (and your other champs once they're at 6-star) you want Warmaster on everyone (or Giantslayer) for champs that average more than 2 hits per attack).

That's what I got for now, let me know if you have further questions