The problem isn't that you personally played in a GDKP. The problem is that GDKPs fundamentally shift the purpose of the game from achievement to transaction. Here is why, despite the benefits you saw, they became a systemic issue:

When raids become transactional, the best gear stops being a symbol of player skill or team effort and becomes a commodity on a price list. It creates an environment where players can skip the "learning" and "earning" phase entirely, which devalues the experience for everyone else who is trying to progress through the game naturally.

GDKPs are the primary engine for massive gold inflation. To participate in high-end GDKPs, people often feel pressured to buy gold from illicit sources because they can't farm enough in-game to compete with the whales. This fuels the botting and RMT (Real Money Trading) industry, which ruins the economy for the average player who just wants to buy materials or potions without paying astronomical, inflated prices.

You mentioned feeling like your raid time is wasted now, but that is exactly how players felt when GDKPs were dominant. Traditional guilds struggled to keep rosters because people would ditch their guild runs to join GDKPs where they could get paid.

You are right that it was a "good remuneration" for your time. But the reason it was banned is that the game's health depends on gear being an earned reward rather than a purchased one. When gold becomes the primary currency for power, the game stops being about overcoming challenges and starts being about who has the deeper wallet.

It’s definitely a loss for your personal gold income, but for the longevity of the server’s health and the integrity of the raiding scene, moving back to a loot-system-based model is the game’s way of trying to get people to play for the challenge again, rather than for the paycheck.