Why is "string" considered a simplified version of "String"?

VS2017-2019 Tools > Options > Text Editor > C# > Code Style (>predefined type preferences:) > For member access expressions

select "Prefer framework type"

---

VS2015 Tools > Options > Text Editor > C# > Code Style

uncheck "Prefer intrinsic predefined type keyword in member access expressions"

---

Example given in VS2015-2019 for this option flips

var local = int.MaxValue (Prefer predefined type /ticked)

to

var local = Int32.MaxValue (Prefer framework type /unticked)

---

ReSharper - to disable it/configure the inspection severity, it is the "Replace built-in type reference with a CLR type name or a keyword" rule.

Now nothing hints at me to change String.Format() to string.Format()

Because you didn't uncheck "Prefer intrinsic predefined type keyword when declaring locals, parameters and members" found under Tools > Options > Text Editor > C# > Code Style

Because it doesn't require using System; at the top.