Also compilers nowadays are smarter and can perform link time optimizations. Meaning that if of a library you only use a single function, in the final executable you would only get that single function. In reality code that use static linking could be more efficient than code that uses dynamic linking.

And you have to consider some performance penalty when using shared libraries. First you have a time penalty when loading the executable, since first you have to run the interpreter (ld-linux) and then your actual code. But also for each function call you have to make an indirect jump into it.