For me, the let down for the Olympic class ships (as well as not having enough lifeboats) was that they had two reciprocating engines which were old technology and I think it should have had triple turbines, as the Lusitania and Mauretania had these in 1907. The Olympic class design was quite conservative.
HMS Dreadnought was the first all turbine warship when it was launched in 1906
I've often pondered the question, "If Titanic had not foundered and had been brought back to H&W repairs, would the total cost have been greater than scrapping the damaged vessel and applying that money to completing Britannic or starting a 4th Olympic class steamer?" It's a hypothetical question with no answer in reality. History does not reveal its alternatives.