Lockdown mode looks very usable despite the messaging that it is "designed for the very few individuals.”
Apple said at the rollout that relatively few people should need this, which is likely correct. The vast majority of people don’t have a state-level attacker going after them.
Also it makes sense that the UI/UX is accessible; many of the people who need this aren’t necessarily tech experts. And even if you are a tech expert, you don’t want a complex UI when you’re under attack.