I'd argue the exact opposite. D2C sets are typically aimed at an older audience. The Keaton Batman films, Back to the Future, Lord of the Rings, the original Jurassic Park films are all properties adults are more familiar with than kids, which is why we got, or are getting, D2C's instead of smaller playsets for those. The X-Men are the exact same case. Adults grew up with the 90's cartoon series, the Fox films, the other cartoon series, etc with while kids today are growing up with The Avengers. So, just from that standpoint, it'd make more sense to release a big X-Men display piece instead of Wolverine's sand buggy, Storm's mech, and Magneto's sailboat of doom.
But, with that said, we're pretty poor predictors of what Lego will do. Most of us thought they would have capitalized on NWH by now. Most of us thought they'd release a modular Avengers Tower before a Black Panther bust. We all thought that new Thanos mold two years back would have seen some sort of reuse. Personally, I would have thought they'd try to capitalize on Teen Titans Go since it's been on for close to 10 years, is aimed at kids, and had a theatrical film release. But, nope. Lego will continue to surprise us for better or worse.