I am a new user (from last five months ), I have seen some users ( I don't want to take their names ) have asked a very very basic question or just definition around 4 or 5 year back, due to these questions their reputation has become in thousands. My question is very clear, Is this thing fair to new users? I am also not interested in getting a high reputation on this site. In my opinion, there should down voting (automatically) also if somebody is there from a very long time not active on this site. There should be some balance between the reputation os new users and older ones. One more thing at present time to get a higher reputation on this site as compared to older times is very tough, So that we also need to take care.
Is it fair? I don't know. Fairness is notoriously subjective. What's fair to one person, is often unfair to another. Since you mention you're new to the community, it might be helpful to first learn what the justification is for the current system. So let me suggest a different question: Does reputation serve its purpose?
What is the purpose of reputation? It's presumably to help the site succeed at its goals. What are the site's goals, you say? I'm glad you asked. In my view, our mission is to build up an archive of high-quality questions and answers that will be useful not only to the person who asked the question, but also to others in the future. This means we want a reputation system that incentivizes behaviors that contributes to that mission, discourages behaviors that don't detract from it, can be implemented in software, and hopefully is as simple as possible. It doesn't need to be perfect as long as it is "good enough".
How well does the current reputation system serve that purpose? It seems to be doing OK, though it's definitely not perfect and it's certainly got some side effects that might be undesirable. What about the specific case of questions that were asked a long time ago -- should they earn more reputation? Maybe. Here are two reasons why that might be reasonable.
First, not all old questions get a lot of upvotes; many don't. When you see an old question with a lot of upvotes, often that is because the question has turned out to be useful to many other visitors -- and in that case it does seem reasonable that it might earn the participants more reputation. You too can ask great questions and post great answers, and if they turn out to be useful to lots of other people, over time they will earn you lots of reputation.
Second, participation in the early days of the site is especially valuable. The early days of a site like this are especially important, because one needs to grow a community. In those days, it was unclear whether the site will succeed or fail; it's one thing to participate when you already know that the site will have a lasting legacy, but people who were participating in the alpha or beta days were doing so at a time when it was unclear whether the site would survive. By participating, they helped the site grow and become attractive to others. So, it doesn't feel unreasonable that users who participated from the start and helped the site get off the ground should be receiving more reputation.
That said, understand that I'm not trying to say the reputation system is perfect. There are a bunch of aspects of it that are known to be odd. Reputation tends to reflect the amount of activity on the site, rather than the knowledge of the participants. There's a lot of randomness; you might write 100 good answers, and one might just happen to get a lot of attention and lots of upvotes. Reputation often isn't correlated to the amount of effort you put in or the difficulty of the answer: sometimes answers to easy questions get a lot of upvotes, because it's easy for everyone to see that they are correct, while a lengthy answer to a hard question might get only a few upvotes because most people don't feel qualified to evaluate it. And Hot Network Questions can distort votes by a large amount.
So there are certainly many aspects of the reputation system that seem odd. But hopefully it averages out in the end, and is "good enough" to help the site succeed.
You asked about removing points from older users who no longer participate. What would the benefit of that be? How would your life be different or better, if someone descended with a magic wand and made that happen? I suspect it would make no difference. For instance, if the older user isn't active any longer, it doesn't matter how much reputation they have. In any case, you can still ask good questions that will be visible to others, contribute to the site by posting good answers, and participate in all the usual ways. What does reputation really do for you? Almost nothing. They're just Internet points. Basically, all reputation does is unlock access to some tools that will help you moderate the site -- but all the most important ways to contribute to the site (ask good questions that will be useful to others and spur good answers; post good answers to other questions; make edits to improve the site) are available to you regardless of reputation.
Lastly, let me suggest a framing for how to think about reputation. It's not a race. Don't think of it as a competition, where the one with the highest rep wins. Rather, think of it as a cooperation. We're all working together to build a great site that will spread knowledge throughout the world, and help others learn computer science. When you see someone else get a bunch of reputation for a good contribution, let's appreciate their contribution and hope they'll come back and keep contributing. And when you see someone get a bunch of reputation for what seems like a poor contribution, well, sometimes that happens, but we shouldn't let it stop us from making the site better.
It's good to have you on the site. I hope you'll stay and continue contributing good content.