Especially a luci theme needs constant attention, or it will break badly. For quite few years, luci development was a bit stagnant l, because the attention was on luci2 as a designated successor - but with that being abandoned in favour if modernizing luci in place, away from router side lua, towards ucode and client-side javascript, development has gotten much more vibrant again in recent years. The cutover from completely cutting the ties with lua has gotten quite close now. All of that has consequences on theming as well, css markup changes and needs fixing, all of which is considerably harder than the rather mechanical 5 minute job of rebuilding the source for apk.
The only constant is change, as you mentioned iptables --> is hard in comparison.