That's amateur fanfic-level writing, at best, and lazy delaying tactic, at worst.
Yeah I'm really starting to get that feeling here. The first few chapters of this were really good, setting up an interesting twist with the male isekai protag-kun getting merc'd and then the kind of heartbreaking dynamic between the two main heroines. It had all it needed to be a powerful, emotional story with just those few details--the innocent girl who perfectly trusts her savior, and the tortured girl with conflicted morals who has to look at her smile and know what she's doing. It's a really strong setup, and was a really interesting take on isekai genre stuff.
But as things have gone on... the pacing has gone completely out of whack, and like Koveras said it's being handled in a very amateurish way. It feels like the author is throwing in new details, powers, or characters for every fight and just putting in the stuff they came up with that they thought was cool, rather than slowly giving us more insight into the mysterious and intriguing power system they'd already set up, with the result that we don't know the stakes or power levels and it feels a little like the author is just telling us about these cool ideas they thought up rather than designing the story for readers. And I see the same thing happening here with plot details, too.
It really feels very undisciplined or insecure, like the author didn't believe in the power of the story they were telling and decided to add Plot and Things Happening. I'll keep reading, and I'd love to see myself proven wrong, but this is shaping up to not be the quality of story I had thought it to be.