That said there are also contexts in which the existing system that was built sucks so bad that rewriting it usually a boon, even if the new wheel sucks, it sucks less from the start.
You at a minimum should engage with the existing wheels and their users to find the ways in which they do and don't work.
In your own time I think it is great to tinker, pull apart, assemble your own things. Every Jedi makes her own light saber right?