I emphatically disagree with your reasoning.
1. Often times, you can't appreciate the existing solution until after you tried to make something better. An awful lot of the people who love Perl love it even more after they spent some time working with Python, Ruby, PHP, or for that matter Java, C#, or Haskell. If a kid - or an old fogey like us - wants to try to make the next Perl? Go for it.
2. Some times, you genuinely do make something that's an evolutionary step forward. What if, 30 years ago, people thinking like you convinced Larry Wall that C + sed + awk was good enough? It's rare, but it does happen.
3. The whole process of trying to understand what came before and trying to do better is an excellent learning method. If I write my own text editor, even if it's awful I'll probably become a better developer.
Now, basing a business model on trumping what came before is like gambling only more stupid. I wouldn't try to get rich inventing the next Perl, the next Facebook, or the next Docker. But trying to make one for fun.... why not?