Don't give a damn to what people say. Front end frameworks are created to make life easy. There's no harm in using them if you understand the core concept that lies behind CSS frameworks.
I have seen employers blindly rejecting people just because their resumes don't contain the words "Bootstrap" or "Foundation". They are hiring people without understanding what Bootstrap and Foundation are. If you are a good front end developer, there are chances that you will get rejected because of this.
In the end, I would say be confident of what you are learning and practising.