Himanshu Tiwari

The reason is, not all programming languages execute at same speed. For example, C is around 5 times faster than Java in most cases.

Also, there are some cases, like in previous month's CodeChef long challenge, where people used PyPy to solve problems using brute force because it was unnecessarily given advantage of higher time limit.

But, in most cases you'll not find any difference in the algorithms used to solve that problem in all languages as their time limits are carefully set.

To learn and get continously better at something, try solving problems that are just higher than your capacity. They should neither be too easy nor too hard for you. 
Choosing such problems is important for growth. Try solving problems on CodeChef by sorting them according to difficulty. You may also try A2OJ to classify problems according to topics and difficulty.

Once you are comfortable with easy problems on these websites, start learning DS and algorithms. Participate in contests and after contest is over, try up-solving the last problem you could not solve during contest. Usually, this is the problem that is just above your capacity.

Problem solving skills.

Most people tend to focus on a specific language, but the most valuable skill you can possibly develop in programming is your logical and analytical ability.

There are multiple ways to do it. Get back to your basics. Know your data structures and algorithms. Start participating in long challenges on CodeChef regularly.

The term "problem solving" may seem very wide, but let me share an incident one of my student shared last week. She happened to have an interview at PayTM, and the interviewer asked her a simple problem regarding the maximum number of overlapping intervals at any point of time in a day. 

The solution was simple to initialize an array for every minute of the day with 0's and incrementing all elements by 1 for each interval range and returning maximum value in array after processing all queries. She was going in the correct direction but discarded the solution due to loop involved for every range. This loop was not even necessary because the queries were offline and she had solved this sub-problem in one of the assignments earlier.  

If you see, it is not about 'knowing' the solution, but about applying/modifying what you know. Knowing any amount of Java will not help if you do not know how to solve a problem.

Any type of 'good' programmers are currently in demand.

By good, I mean people with good analytical and problem solving skills. When a reputed firm hires, they never enforce you to use a specific language to solve a problem. They expect you to learn whatever tech stack they are working on.

The reasoning behind this is, the languages and frameworks change with speed more than you can imagine. Suppose, your project changes from technology A to technology B, it does not make sense to fire the previous developers and hire developers with experience exclusively in B. Most companies, therefore, require good learners and problem solvers.
If you find this answer absurd, feel free to explore interview experiences of companies like Google, Microsoft etc.