But learning the syntax is only a small part of learning a language. Knowing your libraries is a huge part of being productive. How do I do rest queries, cryptography, filesystem manipulations, serialization, spreadsheet manipulations, images manipulations, web frameworks, interaction with the OS, multi-threading debugging, UI, etc. Outside of staying within an ecosystem (JVM / .net), you need to rediscover all these from scratch, get bitten by all the gotchas, etc.