Spin it all you want. I don't consider "thinner is better". I think 5s or even 4 was plenty thin enough. Per that logic, iPhone 14 or so should disappear because it becomes so thin you can't see it anymore. No one griped about 5s being "too thick".
Apple may be satisfied with current battery life but lots of customers are not. If there was an objective "which do you want more?" poll of thinner vs. more battery life, I suspect the results would be pretty dramatic.