Whenever I see double-isekai like this, or (fantasy-to-isekai maybe?), I think of the way the Smartphone WN went. The author Introduced a bunch of characters, including more than a dozen cute girls for the main character to get close to, introduced a huge number of locations and had some big battles in them, but then didn't go into detail exploring ANY of that. Everything is surface-level only. Instead they sent the MC to another isekai world to chase the big-bad. I gave up on it at that point, so I don't know if the story ever got back to the first world, or if MC just started building harems across different parallel universes.
This is at least focusing on cat and elf-girl for the most part, but it still feels like the author started to get pressure to introduce a bunch of new characters and locations at the beginning of the arc. Or maybe they got told, 'You need some more typical isekai elements like a meeting with the gods, forced transmigration,' etc...