inflicting one's incompetence on others
There's nothing wrong with (re)doing old things in new languages as a way to learn. There's nothing wrong with doing things badly as part of the process of learning to do them well. There is, however, something wrong with inflicting your incompetence on others.
Application development tends to have a self-limiting character when it comes to inflicting one's own incompetence on others. People who write bad programs that are meant to be run locally tend to use those programs themselves for a while, suffering the badness themselves, and eventually get better at development as they tweak their programs or abandon them and start over.
Web development is another story entirely, especially where client-side scripting is concerned. Web development encourages people to inflict the disastrous results of their incompetence on others before they even realize how badly they're doing. When things like cross-site scripting, client-side authentication, and other security vulnerabilities come into play, that incompetence can actually harm So what if all it does is spawn sparkly unicorn GIFs in random places on your webpage? It's still programming.
If it has a direct impact on other people, it's highly irresponsible programming.
