re LCS survivability, the problem I have with the complaints is that comparable ships are no better, and in fact in littoral situations are more likely to be worse.

In addition, the Navy identified a hole in strategic operations. They laid out numbers for options that included modding existing ships or building an entire new class. They went with a new class because:
a) it would be better at the identified mission;
b) TCO/life, even taking contract inflation, still made the new ships cheaper. (A big factor here is anticipated lifespan of new ships vs remaining lifespan of existing ships.)
c) They provided an opportunity for large-scale test of modern technologies the navy was considering for service-wide implementation.

(corrected acronym: TCO instead of TOCO)

But I really need to repeat that every option that bases on using an existing or modified existing platform is (with few exceptions) no better at survival while being (varying degrees of) worse at the identified mission.