Actually it depends on the market. Of course WoW is super popular on Western market partly because of Blizzard already had a long successful history in the market. WoW is a great game but even before anyone had a chance to play it, it was hyped as hell just for being based on the world of Warcraft. The source of its hype was there ever since 1994. When RO released, it had nothing like that. But when we take other markets into the context, the popularity of these games like WoW and RO will just become relative. For example, WoW isn’t really popular in Japan and many other Asian as well as generally non-western countries but RO blew these markets and dominated them and Japan is a big market with their own games. And for once RO was the revolution, the start of an era of Asian / Korea / anime-based MMOs to spread worldwide. Before RO, asian MMOs wasn’t really a thing outside of their own countries, MUD games were even more popular at the time in western countries than these “cheesy Asian MMOs” but then RO came and changed that. Also when you reading English gaming websites and commentaries, the more popular ones are mostly US based with the majority of readers coming from the US, they are a bit tad biased toward aged Western games and RO has never been known much there. So saying an MMO is the most successful one globally is of course biased, consider there are just too many aspects to be able to do so fairly.
Back to ToS, in many cases, people mentioning RO when giving feedback for ToS is not because they expect ToS to be another RO but they just want to use the game they have most knowledge about as well as easily be related for other people and the very developers, to use as an example, a reference to point out their mind. So in many case, it’s not that different compared to when someone giving feedback for ToS by referencing to WoW or any other game. Maybe hearing RO over and over again on ToS forum is annoying but I hope we don’t overreact it.
So as I understand, most of us here use WOE purely as a term for a kind of “Guild vs Guild” (*) that involved defending / invasion of “guild” bases, if you play other games with different terms, you might use them and no one shouldn’t judge you for that as long as you try to make it understandable for people who didn’t play the game you referencing to, which the OP clearly did by using the term “castle war” in his post which isn’t exclusive to RO.
(*) Guide or whatever other name they want to call it in the game like faction, it’s the context which is important.
And yes, to be honest, I believe if ToS will ever really be a sky high hit, one important part of its success will be thanks for the support from former RO fans. I know ToS has many references to GE, it is its own game and it is not a successor of RO but whatever it is, we can clearly see the big part of its hype right now is thanks for its “RO vibe”. And just per my reading on the Internet, the reputation of IMC seems be known for being the creator of RO a little bit more than their other games like GE.