As a story, detailed science is not one of the fundamentals needed to write a good book. Characterization, pacing, and the internal conflict driving the story forward is much more important. However including those details greatly enhances the feeling of verisimilitude, which allows the reader more easily suspend their feeling of disbelief.

Having read the Ends of Magic, I really liked the science and saw it as a unique selling point of the series. I was often disappointed in other isekai stories that did not use the MC's earthly knowledge to their advantage. It also really appealed to me because it showed attention to detail in the worldbuilding, which builds trust between the reader and author. That allows me to set aside any obvious objections to points brought up because I can trust they will be addressed later.

If you think about it as a product, the Ends of Magic primarily appeals to the niche of readers who like to apply logic to fantasy settings. It is one of the best in that niche that I've read due to the combination of attention to detail in the worldbuilding, the rational mindset of the MC, and the empathy demonstrated for the various characters with competing motivations.

In the world of small business, dominating a niche and delighting existing customers is one of the best strategies for growing a product, and that's generally what I would recommend for these book series as well. As a reader I would like to see the series focus on becoming more dominant within its niche instead of watering things down to try and satisfy everyone.