Here are the facts: Immediately after RDF was released, WoW had more subscribers than it ever had, despite being in a content drought. This post-RDF period lasted for ~1 year. WotLK lasted for ~2 years.
Therefore, RDF was a tool available for players for about half the lifetime of WotLK and was a major factor in the most successful period in WoW history.
They may have reused code, but they didn’t just write 100 lines in an afternoon and call it a day. Even the most basic project would take more effort than what you are tying to imply.
Retail sucks because the story writing fell off and every expansion has some sort of super grindy borrowed power that disappears with the next expansion. WoW had its peak subscriber count during RDFs time.
The tools are similar, but have some differences. For example, if any player declines in RDF, the entire party goes back to the queue, but for LFR you still start the group if it isn’t full. Also, LFR must consider raid lockouts (RDF up to that point did not have lockouts AFAIK). I’m sure it’s not as easy as just swapping out some variables, but they do likely share a lot of code. I think it’s closer to BG queues than RDF to be honest.
That’s the raid loggers mind set. They think the only content that matters is the latest raid. When I was raiding with my priest I only played her one day a week. The other 5 days I was questing and doing dungeons with the rdf on alts. I spent more time every week in that last year using rdf with my alts then I spent raiding with my main.
There is probably a couple if statements they had to write, and maybe a few methods to handle this interaction, but it really is nothing in comparison to building the tool from scratch.
LFR was so appealing to Blizzard because it took little to no resources to develop it as RDF already existed.
Yes, it grew to 12 million, then did not grow further than that. There is no dispute that this post-RDF period had the most subscribers ever in the history of WoW and did not grow past 12 million.
Do games usually grow during content droughts? The fact that they maintained 12 MILLION SUBSCRIPTIONS during a CONTENT DROUGHT is all you need to know about RDF.
This was the most successful period in WoW history, and this is undisputed. When people talk about “peak WoW” this is the time period they’re talking about. You anti-RDFers are smoking some of the good stuff I guess.