I give this manga a 6.5/10.
The plot is OK in theory, with potential for an 8/10, but the execution has glaring flaws.
Our MC rescues and collects her fave characters from various franchises, but how do these franchises fit together?
It would be so easy to say "this is the shared world of game company X, spanning Y games complete with Z novel tie-ins."
But if you don't, you need to account for why the names and locations are different between the story and reality.
The thing with the demon lord betrayal, in particular, felt rushed and unsatisfactory.
You can't just claim that the elf guy's best friend will betray him "because he's a demon" and have him believe it instantly without proof and then go serve the accuser loyally.
It's not like proof of betrayal would be that hard to add in for the author - I guess they just didn't see an issue.
Over all, the manga is a frustrating read because all it would take to make it good is some minor changes - some added panels, some text being different. Feels like watching someone sculpt clay while wearing boxing gloves.