Well let's map it out a bit.
DLC Characters carried by fan demand:
Inarguably, Banjo is here because he was highly requested. No new games or anything, this was just a character who had a steady twenty years of heavy fan demand known to both Nintendo and Microsoft. No doubt Banjo performed well on the ballot, too.
Debatable:
I'm certain there had always been demand for DQ in Smash overseas, and I know that many people wanted to see Steve with the first wave. The reason they're here in the grey area is that I'm not convinced that was particularly the reason they got added. DQ and Minecraft are big enough where I can't imagine they actually needed people to ask for them to make it, so to say it's explicitly in response to fan demand feels disingenuous.
Sephiroth is here because I saw him place in a couple Japanese polls and I dunno, maybe he had a stronger push over there. Barely any serious discussion over here, most people didn't even bother humoring the possibility.
All three of these characters are VERY popular in their own right, but since your frame of reference was Ridley / K Rool / Banjo I don't believe they qualify. These three characters were longstanding wishes amongst the core Smash community, while these characters are moreso popular to a wide general audience by virtue of being from immensely popular and successful franchises.
The goal here was less to cater to that pool of people requesting the aforementioned characters and moreso reaching people more on a surface level.
Definitely Not:
These characters saw barely any serious discussion regarding inclusion in Smash and were far detached from the "fan favorite" wishes of the community. You had a few prominent voices in the Smash community vouching for Joker, but not a whole lot who took the idea as anything more than a pipe dream. Half of the people in the community didn't even know who the hell Terry was.
It's not to say any of these characters who I didn't put in the first category are not popular and well loved additions
now. Just that many of them weren't seeing any serious conversation until leaks popped up with them in it or they were formally revealed to everyone's surprise. I'm not one of those guys who is gonna say "since [x character] is popular and expected they're definitely not gonna make it", but I'm surprised to hear someone express the sentiment that sheer fan demand makes a character more likely at
this point. For the base roster, definitely. Very debatable for DLC, and I don't agree with the idea that "most third parties" reflect this at all.