You can only become a great developer by putting the effort in. Imagine for a moment — You can’t become fit physically by reading a lot about fitness. You actually need to go to the gym and put the hours and sweat in! Same concept applies for coding as well.
…the ’90s single threaded environment. Most of those programming languages supports multi-threading. But the real problem comes with concurrent execution, threading-locking, race conditions and deadlocks. Those things make it hard to create a multi-threading application on those languages.