Plagiarism isn’t the issue here as that isn’t even the assertion of this sentence. The assertion of this sentence is that copied work is “mediocre”. That is a 100% baseless assertion and is very incorrect. Most good code is reused precisely because it is good code. The better the code the more it will be reused and adapted. Only a fool would rewrite something that already exists in its most optimized form. Reuse and adaptation has been the essence of software development for 60 years and that’s never going to change. Frankly put, a software developer that insists on writing everything from scratch is just to inefficient to be employable.