It's not hard to agree that there is nothing wrong with looking at the past and reminiscing of better times or to prefer a certain past era. For example, there is nothing bad about thinking of the old web, its culture, and memes, and wishing we could still have some of that. There are just so many good things from back then, many worth imitating and reviving! However, when you do nothing but think and, worse, complain about it, then you have a problem.
What's the difference between the usual nostalgic and the OC creator of before? They were clearly both around at the same time and enjoyed the same stories and jokes; in fact, there is a chance they were both the same person. Yet today the nostalgic will only wallow in reminiscence without doing anything else. Hopelessly enamored by what has already been made, the nostalgic is forever stuck in a loop of inaction: things were so good before and so bad now, so why bother creating?
For example, you might be familiar with DESU-posting, a vintage imageboard classic. The nostalgic loves DESU-posting so he tries to bring it back, like so:
DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU DESU
However, what is the purpose of spamming DESU nowadays if not for nostalgia masturbation? A homage? It's preaching to the choir! The nostalgic is usually not creating anything new or interesting, like DESU-posting was back then. He desperately tries to bring back ingenuine calques of old web traditions, without understanding what made them good in the first place: freedom, authenticity, and novelty. The nostalgic will keep ignoring the lessons he should have learned from the creation of those traditions he loves so much and not make anything memorable himself, and he'll simply keep consuming more of what's already good, stuck on yet another loop, and complain that things were good then but they suck now. Oh, poor and innocent nostalgic, so helpless and powerless, there's nothing he can do about it!
Sometimes it's even worse: precisely because he lacks the understanding of what made the past good, the nostalgic's imitations end up as parodies instead of homages. Think, as an example, of the thousands of awful faux-pixel art games that were making the rounds a few years ago.
On the opposite side of the spectrum there is the "anti-nostalgic", someone who denigrates the past and doesn't feel its values are worth considering. Think of contemporary architects: they disregard the tenets of classical architecture, and purposely ignoring its lessons, they create from scratch just for the sake of experimentation and progress just because they can.
Both the nostalgic and the anti-nostalgic mindsets are degenerate and stagnant. One is obsessed with the past and dwells in it, hoping to return without understanding (or even wanting to understand) that it is he who could be remaking it anew, so he doesn't do anything, and everything he knows fades away. The other hates the past so much he doesn't want to learn any lessons from it, so he creates without purpose, commits known mistakes, and alienates communities. Both are wrong exactly because they both refuse to understand the past.
Excessive nostalgia hurts the nostalgic the most, when so surrounded by inspirations he could be bringing so much new joy and fun to people's lives, just as OC creators did! And in the end, it's the nostalgic's very inaction that has killed the culture whose demise he so regrets!
Don't get me wrong, though; although it's clear that we can't go back and shouldn't cry about it all day, we can and must bring it back. We can and must revisit the past and take back with us the good things to the present. Yet we must do so properly. We must learn from the past and try to gain a deep understanding of its values and lessons, and build new things inspired by it, paying tribute to what's brought us joy, while keeping moving forward. That is the only way the old culture, so beloved, will reflourish.
Nostalgic, you must realize that you, too, can create and make lovable new things with the same soul as the classics and it's you who will revive everything good. First, you must stop being idle, and stop complaining about past stuff you can't change. Instead you should do something, anything! But most importanly, be authentic. Don't mock and parody, and, eventually, others will also fondly remember what you made, just as you fondly remember what is in the past.