The pacing is bad.
As many pages there are per chapter, there should be more development with the main characters. The MC gets an okay amount, but no one else in the main cast does.
The plot arc is awkward in many areas, either too wordy, too fast, or just filler. Again bad pacing.
Most recent chapters, 20 - 25 are spent on a conflict between the regular people (of the island) and fantasy people and a child lost at sea. That's over 100 pages, fleshing out a side character's arc.
Not the MC. Not his elf waifu, childhood friend waifu, onee waifu, or Government OL waifu. A loli side character. Actually no, the loli get introduced much earlier on, so closer to 150 pages on her.
I get that Japan's (and some of y'all) got a thing for lolis, but c'mon.
If a setting has weak characters, then the scenario and world building needs to drive the story. If the world building or background is weak, then the character interaction and development needs to drive the story. This manga waffles between both and does so poorly.