The term “full-stack developer” implies that a developer is equally adept at both frontend code and backend code, but I’ve never in my personal experience witnessed anyone who truly fits that description.
In many of the descriptions I’ve seen it goes even further than that. Sometimes full-stack developer refers to someone who can also administer server architectures or cloud services or do database work.
There are certainly a number of people who can fumble their way through all of these things. I consider myself one of them. But I wouldn’t call myself great or even very good at any one of them. There is nearly no one that is great at all of these things. I’ve only seen perhaps one or two in over 20 years of banging away at this keyboard.
This is also an excellent point from Brad:
Large organizations have the ability to hire specialists, which is why I get so confused why so many companies proudly declare they only hire full-stack developers. Having team members that can own the frontend experience is a good thing. Having team members that can own all things backend is a good thing. Having everyone work together to create successful products is a good thing.
No one should be ashamed that they are very good at one thing and not as good at another. Embrace that fact and become an expert.